Annual Report by Investment Company (Form N-CSR)

Putnam Municipal
Opportunities
Trust

Annual report
4 | 30 | 22

The fund has adopted a managed distribution policy (the "Distribution Policy") with the goal of providing shareholders with a consistent, although not guaranteed, monthly distribution. In accordance with the Distribution Policy, the fund currently expects to make monthly distributions to common shareholders at a distribution rate per share of $0.0531. Distributions may include ordinary and/or tax-exempt income, net capital gains, and/or a return of capital of your investment in the fund. You should not draw any conclusions about the fund's investment performance from the amount of this distribution or from the terms of the Distribution Policy. The Distribution Policy provides that the Board of Trustees may amend or terminate the Distribution Policy at any time without prior notice to fund shareholders.

Message from the Trustees

June 14, 2022

Dear Fellow Shareholder:

The year to date has been difficult for investors, with bond and stock prices falling in repeated market downturns. Inflation has climbed to levels not seen in decades, prompting the U.S. Federal Reserve to reverse the stimulus that had helped support financial assets since 2020. Markets globally also have reacted to the Russia-Ukraine War and the worsening Covid-19 pandemic in China. In the underlying economy, we have seen encouraging signs, such as abundant job openings and wage gains in the United States.

History has shown us that markets eventually recover from crises and may reward those focused on long-term goals rather than short-term uncertainties. At Putnam, professional, active investors are working for you. They are monitoring risks while looking for strong potential investments for your fund. Learn more in the interview with your fund manager(s) in the following pages.

Thank you for investing with Putnam.

Putnam Municipal Opportunities Trust has the flexibility to invest in municipal bonds issued by any U.S. state or territory. As a closed-end fund, it shares some common characteristics with open-end mutual funds, but there are some key differences that investors should understand as they consider their portfolio.

Looking at a closed-end fund's performance

You will usually see that the NAV and the market price differ. The market price can be influenced by several factors that cause it to vary from the NAV, including fund distributions, changes in supply and demand for the fund's shares, changing market conditions, and investor perceptions of the fund or its investment manager.

A mix of credit qualities

In addition to its flexible geographical focus, Putnam Municipal Opportunities Trust combines bonds of differing credit quality. The fund invests in high-quality bonds, but also includes an allocation to lower-rated bonds, which may offer higher income in return for more risk.

Data are historical. Past performance does not guarantee future results. More recent returns may be less or more than those shown. Investment return and net asset value will fluctuate, and you may have a gain or a loss when you sell your shares. Performance assumes reinvestment of distributions and does not account for taxes. Fund returns in the bar chart are at NAV. See below and pages 10-11 for additional performance information, including fund returns at market price. Index and Lipper results should be compared with fund performance at NAV. Fund results reflect the use of leverage, while index results are unleveraged and Lipper results reflect varying use of, and methods for, leverage.

All Bloomberg indices are provided by Bloomberg Index Services Limited.

Lipper peer group average is provided by Lipper, a Refinitiv company.

This comparison shows your fund's performance in the context of broad market indexes for the 12 months ended 4/30/22. See above and pages 10-11 for additional fund performance information. Index descriptions can be found on page 17.

All Bloomberg indices are provided by Bloomberg Index Services Limited.

Paul, how did municipal bonds perform during the 12-month period ended April 30, 2022?

Municipal bonds began the period on solid ground, supported by positive supply/demand technicals, low interest rates, and strong economic growth. In the second half of the period, market conditions became more challenging. Investors feared that persistently high inflation might prompt the Federal Reserve to pare back pro-growth monetary policies faster than expected. Inflation concerns were stoked by supply chain disruptions, rising labor costs, and higher commodity prices. Geopolitical and economic uncertainties surrounding Russia's invasion of Ukraine in February 2022 also unnerved investors.

At their March 2022 meeting, Fed policymakers raised their benchmark interest rate by a quarter percentage point and signaled their intent to take further measures to curb the highest inflation in 40 years. The markets began pricing in a higher probability that the Fed would raise interest rates more aggressively. At the May 2022 meeting [shortly after the close of the fund's reporting period], Fed officials raised their key rate by half a percentage point, the

Credit qualities are shown as a percentage of the fund's net assets (common and preferred shares) as of 4/30/22. A bond rated BBB or higher (SP-3 or higher, for short-term debt) is considered investment grade. This chart reflects the highest security rating provided by one or more of Standard & Poor's, Moody's, and Fitch. Ratings may vary over time.

Cash and net other assets, if any, represent the market value weights of cash, derivatives, and short-term securities in the portfolio. The fund itself has not been rated by an independent rating agency.

Top 10 state allocations are shown as a percentage of the fund's net assets (common and preferred shares) as of 4/30/22. As of 4/30/22, the fund did not have any investments in Puerto Rico. Summary information may differ from the portfolio schedule included in the financial statements due to the differing treatment of interest accruals, the floating-rate portion of tender option bonds, derivative securities, if any, and the use of different classifications of securities for presentation purposes. Holdings and allocations may vary over time.

largest hike in 22 years. The Fed also announced that it would begin reducing bond holdings on its balance sheet on June 1, 2022.

These actions led to significant outflows from municipal bond funds, resulting in increasingly difficult market technicals. For the 12 months ended April 30, 2022, the Bloomberg Municipal Bond Index [the fund's benchmark] returned -7.88%. Short-term municipal bonds outperformed intermediate- and long-term cohorts. From a credit perspective, investment-grade municipal bonds held up better than higher-yielding, lower-rated municipal bonds in the risk-off environment.

How did the fund perform during the reporting period?

For the 12 months ended April 30, 2022, the fund underperformed its benchmark, a non-leveraged index, due to our leveraging strategies. The fund's return was close to that of the median fund ranked within its Lipper peer group, General & Insured Municipal Debt Funds [leveraged closed-end]. [Median is the midpoint in a series of values laid out in numerical order.]

What strategies or holdings influenced the fund's performance during the period?

With the significant sell-off in fixed income in early 2022, we believed municipal bonds had become more attractive. We extended the portfolio's duration, a measure of the fund's interest-rate sensitivity. At period-end, the fund's duration was modestly long relative to the level of its Lipper peer group. We believe this positioning may help the fund outperform if the year-to-date rise in interest rates reverses course.

At period-end, the fund held an overweight exposure to bonds rated A and BBB relative to the benchmark. From a sector- or industry-positioning perspective, we favored continuing-care retirement communities, water/sewer, and charter school bonds relative to the fund's Lipper peer group.

Regarding our strategy for state debt, the fund held an overweight exposure to Illinois relative to its Lipper peer group. We believe Illinois's financial profile continues to stabilize, and its flexibility and credit fundamentals have improved since the onset of the Covid-19 pandemic in the United States.

The fund remained underweight in its exposure to uninsured Puerto Rico municipal debt relative to its Lipper peer group. At period-end, the fund had no holdings in bonds issued by Puerto Rico. However, we have become somewhat more optimistic about the U.S. territory's credit fundamentals. In March 2022, Puerto Rico ended its nearly five-year bankruptcy with a plan to restructure its debt, resume payments to bondholders, and restore its public pension system. We continue to monitor Puerto Rico-related debt for potential investment opportunities.

How did you use derivatives during the period?

We utilized swaps to hedge or gain exposure to interest-rate and term structure risk and to hedge or gain exposure to inflation. Additionally, we used futures for hedging Treasury term structure risk and yield curve positioning.

What were the fund's distributions during the period?

The fund's distributions are fixed at a targeted rate. The targeted rate is not expected to vary with each distribution but may change from time to time. During the last fiscal year, the fund made monthly distributions totaling $0.6372 per share, which were characterized as $0.2331 per share of net realized gain, and $0.4041 per share of net investment income. While there

were no distributions of capital during the fiscal year, distributions of capital decrease the fund's total assets and total assets per share and, therefore, could have the effect of increasing the fund's expense ratio. In general, the policy of fixing the fund's distributions at a targeted rate does not affect the fund's investment strategy. However, in order to make these distributions, on occasion the fund may have to sell portfolio securities at a less than opportune time. [Please see the Distributions to shareholders note on page 56 for more information on fund distributions.]

What is your current assessment of the health of the municipal bond market?

Municipal bonds have faced headwinds so far in 2022 as positive seasonal factors waned, fund flows turned negative, and the market adjusted to a quicker pace of monetary policy normalization. However, municipal credit fundamentals remain strong, in our view. Unprecedented fiscal support, tax revenue outperformance, and strong economic growth expectations put most state and local governments in their best fiscal shape for more than a decade. State and local tax collections also were up 13.6% in 2021 compared with 2020. Finally, municipal defaults are running below long-term averages year to date through April 30, 2022, and remain isolated to the lowest-rated cohorts. As such, we believe the credit outlook is currently the most favorable factor supporting the asset class.

What is your outlook?

Higher-than-expected inflation and strong labor reports during the early months of 2022 have seemingly cemented the Fed's pivot to a hawkish stance. The market has quickly repriced to reflect a faster pace of policy normalization. In our view, the Fed is likely to continue the path of monetary policy normalization. We believe this process could contribute to heightened market volatility but also present investors with attractive opportunities.

We expect pandemic-related supply chain pressures will begin to ease and U.S. economic activity will slow in the second half of 2022. We think the combination could contribute to slower growth and lower inflation, which

This chart shows how the fund's top weightings have changed over the past six months. Allocations are shown as a percentage of the fund's net assets (common and preferred shares). Current period summary information may differ from the information in the portfolio schedule notes included in the financial statements due to the inclusion of derivative securities, any interest accruals, the timing of matured security transactions, the use of different classifications of securities for presentation purposes, and rounding. Holdings and allocations may vary over time.

could lead to a slower pace of monetary policy normalization than is currently priced in.

Although supply/demand technicals remain challenged, we believe credit fundamentals are strong and valuations are attractive. Future returns look more promising for longer-term investors, in our opinion.

Thank you, Paul, for your time and insights today.

The views expressed in this report are exclusively those of Putnam Management and are subject to change. Disclosures provide only a summary of certain changes that have occurred in the past fiscal period, which may not reflect all of the changes that have occurred since an investor purchased the fund. They are not meant as investment advice.

Please note that the holdings discussed in this report may not have been held by the fund for the entire period. Portfolio composition is subject to review in accordance with the fund's investment strategy and may vary in the future. Current and future portfolio holdings are subject to risk. Statements in the Q&A concerning the fund's performance or portfolio composition relative to those of the fund's Lipper peer group may reference information produced by Lipper Inc. or through a third party.

HOW CLOSED-END FUNDS DIFFER FROM OPEN-END FUNDS

Closed-end funds and open-end funds share many common characteristics but also have some key differences that you should understand as you consider your portfolio strategies.

More assets at work Open-end funds are subject to ongoing sales and redemptions that can generate transaction costs for long-term shareholders. Closed-end funds, however, are typically fixed pools of capital that do not need to hold cash in connection with sales and redemptions, allowing the funds to keep more assets actively invested.

Traded like stocks Closed-end fund shares are traded on stock exchanges and, as a result, their prices fluctuate because of the influence of several factors.

They have a market price Like an open-end fund, a closed-end fund has a per-share net asset value (NAV). However, closed-end funds also have a "market price" for their shares - which is how much you pay when you buy shares of the fund, and how much you receive when you sell them.

When looking at a closed-end fund's performance, you will usually see that the NAV and the market price differ. The market price can be influenced by several factors that cause it to vary from the NAV, including fund distributions, changes in supply and demand for the fund's shares, changing market conditions, and investor perceptions of the fund or its investment manager. A fund's performance at market price typically differs from its results at NAV.

Your fund's performance

This section shows your fund's performance, price, and distribution information for periods ended April 30, 2022, the end of its most recent fiscal year. In accordance with regulatory requirements for mutual funds, we also include performance information as of the most recent calendar quarter-end. Performance should always be considered in light of a fund's investment strategy. Data represent past performance. Past performance does not guarantee future results. More recent returns may be less or more than those shown. Investment return, net asset value, and market price will fluctuate, and you may have a gain or a loss when you sell your shares.

Fund performance Total return and comparative index results for periods ended 4/30/22

Performance assumes reinvestment of distributions and does not account for taxes.

Index and Lipper results should be compared with fund performance at net asset value. Fund results reflect the use of leverage, while index results are unleveraged and Lipper results reflect varying use of, and methods for, leverage.

Lipper peer group average is provided by Lipper, a Refinitiv company.

All Bloomberg indices are provided by Bloomberg Index Services Limited.

^* Over the 1-year, 3-year, 5-year, 10-year, and life-of-fund periods ended 4/30/22, there were 58, 51, 49, 44, and 23 funds, respectively, in this Lipper category.

Performance includes the deduction of management fees and administrative expenses.

Past performance does not indicate future results.

Fund price and distribution information For the 12-month period ended 4/30/22

The classification of distributions, if any, is an estimate. Final distribution information will appear on your year-end tax forms.

¹ For some investors, investment income may be subject to the federal alternative minimum tax. Income from federally exempt funds may be subject to state and local taxes.

² Capital gains, if any, are taxable for federal and, in most cases, state purposes.

³ Most recent distribution, including any return of capital and excluding capital gains, annualized and divided by NAV or market price at end of period.

⁴ Assumes maximum 40.80% federal tax rate for 2022. Results for investors subject to lower tax rates would not be as advantageous.

Fund performance as of most recent calendar quarter Total return for periods ended 3/31/22

See the discussion following the fund performance table on page 10 for information about the calculation of fund performance.

Information about the fund's goal, investment strategies, principal risks, and fundamental investment policies

Goal

The goal of the fund is to seek as high a level of current income exempt from federal income tax as we believe to be consistent with preservation of capital.

The fund's main investment strategies and related risks

This section contains detail regarding the fund's main investment strategies and the related risks you face as a fund shareholder. It is important to keep in mind that risk and reward generally go hand in hand; the higher the potential reward, the greater the risk.

The fund intends to achieve its objective by investing in a portfolio of investment-grade and some below investment-grade municipal bonds selected by Putnam Management. The fund also uses leverage, primarily by issuing preferred shares in an effort to enhance the returns for the common shareholders. The fund's shares trade on a stock exchange at market prices, which may be lower than the fund's net asset value. The fund's use of leverage involves risks, which are discussed in more detail below, and may increase the volatility of the fund's net asset value.

• Tax-exempt investments. These investments are issued by or for states, territories or possessions of the United States or by their political subdivisions, agencies, authorities or other government entities, and the income from these investments is exempt from federal income tax. These investments are issued to raise money for public purposes, such as loans for the construction of housing, schools or hospitals, or to provide temporary financing in anticipation of the receipt of taxes and other revenue. They also include private activity obligations of public authorities to finance privately owned or operated facilities. Changes in law or adverse determinations by the Internal Revenue Service could make the income from some of these obligations taxable.

• Alternative minimum tax risk. The fund may invest in municipal securities and private activity bonds that generate interest that is subject to federal alternative minimum tax (AMT). As a result, taxpayers who are subject to the AMT potentially could earn a lower after-tax return. Corporate shareholders will be required to include all exempt interest dividends in determining their federal AMT. For more information, including possible state, local and other taxes, contact your tax advisor.

• General obligations. These are backed by the issuer's authority to levy taxes and are considered an obligation of the issuer. They are payable from the issuer's general unrestricted revenues, although payment may depend upon government appropriation or aid from other governments. These investments may be vulnerable to legal limits on a government's power to raise revenue or increase taxes, as well as economic or other developments that can reduce revenues.

• Revenue obligations. These are payable from revenue earned by a particular project or other revenue source. They include private activity bonds such as industrial development bonds, which are paid only from the revenues of the private owners or operators of the facilities. Investors can look only to the revenue generated by the project or the private company operating the project rather than the credit of the state or local government authority issuing the bonds. Revenue obligations are typically subject to greater credit risk than general obligations because of the relatively limited source of revenue.

• Tender option bonds. The fund may leverage its assets through the use of proceeds received through tender option bond transactions. In a tender option bond transaction, the fund transfers a fixed-rate municipal bond to a special purpose entity trust (TOB trust) sponsored by a broker. The TOB trust funds the purchase of the fixed rate bonds by issuing short-term floating-rate bonds to third parties and allowing the fund to retain the residual interest in the TOB trust's assets and cash flows, which are in the form of inverse floating rate bonds. The inverse floating rate bonds held by the fund give the fund the right to (1) cause the holders of the floating rate bonds to tender their notes at par, and (2) to have the fixed-rate bond held by the TOB trust transferred to the fund, causing the TOB trust to be liquidated. The fund will look through to the underlying municipal bond held by a TOB trust for purposes of the fund's 80% policy referenced below under the heading "The fund's fundamental investment policies."

• Interest rate risk. The values of bonds and other debt instruments usually rise and fall in response to changes in interest rates. Interest rates can change in response to the supply and demand for credit, government and/or central bank monetary policy and action, inflation rates, and other factors. Declining interest rates generally result in an increase in the value of existing debt instruments, and rising interest rates generally result in a decrease in the value of existing debt instruments. Changes in a debt instrument's value usually will not affect the amount of interest income paid to the fund, but will affect the value of the fund's shares. Interest rate risk is generally greater for investments with longer maturities.

Some investments give the issuer the option to call or redeem an investment before its maturity date. If an issuer calls or redeems an investment during a time of declining interest rates, we might have to reinvest the proceeds in an investment offering a lower yield, and, therefore, the fund might not benefit from any increase in value as a result of declining interest rates.

• Credit risk. Investors normally expect to be compensated in proportion to the risk they are assuming.

Thus, debt of issuers with poor credit prospects usually offers higher yields than debt of issuers with more secure credit. Higher-rated investments generally have lower credit risk.

We invest mainly in investment-grade debt investments. These are rated at least BBB or its equivalent at the time of purchase by a nationally recognized securities rating agency, or are unrated investments that we believe are of comparable quality. We may invest up to 30% of the fund's total assets in non-investment-grade investments. However, we will not invest in investments that are rated lower than BB or its equivalent by each agency rating the investment, or are unrated securities that we believe are of comparable quality. We will not necessarily sell an investment if its rating is reduced after we buy it.

We may also invest in investment that are below-investment-grade (sometimes referred to as "junk bonds"), which can be more sensitive to changes in markets, credit conditions, and interest rates and may be considered speculative. These investments are rated below BBB or its equivalent, which reflects a greater possibility that the issuers may be unable to make timely payments of interest and principal and thus default. If default occurs, or is perceived as likely to occur, the value of the investment will usually be more volatile and is likely to fall. The value of a debt instrument may also be affected by changes in, or perceptions of, the financial condition of the issuer, borrower, counterparty, or other entity, or underlying collateral or assets, or changes in, or perceptions of, specific or general market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. A default or expected default could also make it difficult for us to sell the investment at a price approximating the value we had previously placed on it. Tax-exempt debt, particularly lower-rated tax-exempt debt, usually has a more limited market than taxable debt, which may at times make it difficult for us to buy or sell certain debt instruments or to establish their fair value. Credit risk is generally greater for investments that are required to make interest payments only at maturity rather than at intervals during the life of the investment.

Bond investments may be more susceptible to downgrades or defaults during economic downturns or other periods of economic stress, which in turn could affect the market values and marketability of many or all bond obligations of issuers in a state, U.S. territory, or possession. For example, the novel coronavirus (Covid-19) pandemic has significantly stressed the financial resources of many tax-exempt debt issuers. This may make it less likely that those issuers can meet their financial obligations when due and may adversely impact the value of their bonds, which could negatively impact the performance of the fund. In light of the uncertainty surrounding the magnitude, duration, reach, costs and effects of the Covid-19 pandemic, as well as actions that have been or could be taken by governmental authorities or other third parties, it is difficult to predict the level of financial stress and duration of such stress issuers may experience. We may buy investments that are insured as to the payment of principal and interest in the event the issuer defaults. Any reduction in the insurer's ability to pay claims may adversely affect the value of insured investments and, consequently, the value of the fund's shares.

• Focus of investments. We may make significant investments in a particular segment of the tax-exempt debt market, such as tobacco settlement bonds or revenue bonds for health care facilities, housing or airports. We may also make significant investments in the debt of issuers located in the same state. These investments may cause the value of the fund's shares to fluctuate more than the values of shares of funds that invest in a greater variety of investments. Certain events may adversely affect all investments within a particular market segment. Examples include legislation or court decisions, concerns about pending legislation or court decisions, and lower demand for the services or products provided by a particular market segment. Investing in issuers located in the same state may make the fund more vulnerable to that state's economy and to factors affecting its tax-exempt issuers, such as their ability to collect revenues to meet payment obligations.

At times, the fund and other accounts that Putnam Management and its affiliates manage may own all or most of the debt of a particular issuer. This concentration of ownership may make it more difficult to sell, or to determine the fair value of, these investments.

• Derivatives. We may engage in a variety of transactions involving derivatives, such as futures, options, swap contracts and inverse floaters, although they do not represent a primary focus of the fund. Derivatives are financial instruments whose value depends upon, or is derived from, the value of something else, such as one or more underlying investments, pools of investments or indexes. We may make use of "short" derivatives positions, the values of which typically move in the opposite direction from the price of the underlying investment, pool of investments, or index. We may use derivatives both for hedging

and non-hedging purposes, such as to modify the behavior of an investment so that it responds differently than it would otherwise respond to changes in a particular interest rate. For example, derivatives may increase or decrease an investment's exposure to long- or short-term interest rates or cause the value of an investment to move in the opposite direction from prevailing short-term or long-term interest rates. We may also use derivatives as a substitute for a direct investment in the securities of one or more issuers. However, we may also choose not to use derivatives, based on our evaluation of market conditions or the availability of suitable derivatives. Investments in derivatives may be applied toward meeting a requirement to invest in a particular kind of investment if the derivatives have economic characteristics similar to that investment.

Derivatives involve special risks and may result in losses. The successful use of derivatives depends on our ability to manage these sophisticated instruments. Some derivatives are "leveraged," which means they provide the fund with investment exposure greater than the value of the fund's investment in the derivatives. As a result, these derivatives may magnify or otherwise increase investment losses to the fund. The risk of loss from certain short derivatives positions is theoretically unlimited. The value of derivatives may move in unexpected ways due to the use of leverage or other factors, especially in unusual market conditions, and may result in increased volatility.

Other risks arise from the potential inability to terminate or sell derivatives positions. A liquid secondary market may not always exist for the fund's derivatives positions. In fact, many over-the-counter instruments (investments not traded on an exchange) will not be liquid. Over-the-counter instruments also involve the risk that the other party to the derivatives transaction will not meet its obligations.

• Preferred share leverage risk. Leverage from the issuance of preferred shares creates risks, including the likelihood of greater volatility of net asset value and market price of, and distributions from, the fund's common shares and the risk that fluctuations in dividend rates on preferred shares may affect the return to common shareholders. If the income from the investments purchased with proceeds received from leverage is not sufficient to cover the cost of leverage, the amount of income available for distribution to common shareholders will be less than if leverage had not been used. While the fund has preferred shares outstanding, an increase in short-term interest rates could result in an increased cost of leverage, which could adversely affect the fund's income available for distribution to common shareholders. In connection with its preferred shares, the fund is required to maintain specified asset coverage mandated by applicable federal securities laws and by the fund's Amended and Restated Bylaws. The fund may be required to dispose of portfolio investments on unfavorable terms if market fluctuations or other factors cause the required asset coverage to be less than the prescribed amount. There can be no assurance that a leveraging strategy will be successful.

• Liquidity and illiquid investments. We may invest in illiquid investments, which may be considered speculative and which may be difficult to sell. The sale of many of these investments is prohibited or limited by law or contract. Some investments may be difficult to value for purposes of determining the fund's net asset value. Certain other investments may not have an active trading market due to adverse market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, including investors trying to sell large quantities of a particular investment or type of investment, or lack of market makers or other buyers for a particular investment or type of investment. We may not be able to sell the fund's illiquid investments when we consider it desirable to do so, or we may be able to sell them only at less than their value.

• Market risk. The value of investments in the fund's portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions (including perceptions about monetary policy, interest rates or the risk of default); government actions (including protectionist measures, intervention in the financial markets or other regulation, and changes in fiscal, monetary or tax policies); geopolitical events or changes (including natural disasters, epidemics or pandemics, terrorism and war); and factors related to a specific issuer, geography, industry or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund's portfolio holdings. These risks may be exacerbated during economic downturns or other periods of economic stress.

The novel coronavirus (Covid-19) pandemic and efforts to contain its spread have negatively affected, and are likely to continue to negatively affect, the global economy, the economies of the United States and other individual countries, and the financial performance of individual issuers, sectors, industries, asset classes, and markets in significant and unforeseen ways. The Covid-19 pandemic has resulted in significant market volatility, exchange trading suspensions and closures, declines in global financial markets, higher default rates, and economic downturns and recessions, and these effects may continue for an extended period of time and may increase in severity over time. In addition, actions taken by government and quasi-governmental authorities and regulators throughout the world in response to

the Covid-19 pandemic, including significant fiscal and monetary policy changes, may affect the value, volatility, and liquidity of some securities and other assets. Given the significant uncertainty surrounding the magnitude, duration, reach, costs and effects of the Covid-19 pandemic, as well as actions that have been or could be taken by governmental authorities or other third parties, it is difficult to predict its potential impacts on the fund's investments. The effects of the Covid-19 pandemic also are likely to exacerbate other risks that apply to the fund, including the risks disclosed in the fund's prospectus, which could negatively impact the fund's performance and lead to losses on your investment in the fund.

• Management and operational risk. The fund is actively managed and its performance will reflect, in part, our ability to make investment decisions that seek to achieve the fund's investment objective. There is no guarantee that the investment techniques, analyses, or judgments that we apply in making investment decisions for the fund will produce the intended outcome or that the investments we select for the fund will perform as well as other securities that were not selected for the fund. As a result, the fund may underperform its benchmark or other funds with a similar investment goal and may realize losses. In addition, we, or the fund's other service providers, may experience disruptions or operating errors that could negatively impact the fund. Although service providers may have operational risk management policies and procedures and take appropriate precautions to avoid and mitigate risks that could lead to disruptions and operating errors, it may not be possible to identify all of the operational risks that may affect the fund or to develop processes and controls to completely eliminate or mitigate their occurrence or effects.

• Other investments. In addition to the main investment strategies described above, the fund may also make other types of investments, which may produce taxable income and be subject to other risks. The fund may also invest in cash or cash equivalents, including money market instruments or short-term instruments such as commercial paper, bank obligations (e.g., certificates of deposit and bankers' acceptances), repurchase agreements, and U.S. Treasury bills or other government obligations. The fund may also from time to time invest all or a portion of its cash balances in money market and/or short-term bond funds advised by Putnam Management or its affiliates. The percentage of the fund invested in cash and cash equivalents and such money market and short-term bond funds is expected to vary over time and will depend on various factors, including market conditions and our assessment of the cash level that is appropriate to allow the fund to pursue investment opportunities as they arise. Large cash positions may dampen performance and may prevent the fund from achieving its goal.

• Temporary defensive strategies. In response to adverse market, economic, political or other conditions, we may take temporary defensive positions, such as investing some or all of the fund's assets in cash and cash equivalents, that differ from the fund's usual investment strategies. However, we may choose not to use these temporary defensive strategies for a variety of reasons, even in very volatile market conditions. If we do employ these strategies, the fund may miss out on investment opportunities and may not achieve its goal. Additionally, while temporary defensive strategies are mainly designed to limit losses, they may not work as intended.

• Changes in policies. The Trustees may change the fund's goal, investment strategies and other policies without shareholder approval, except in circumstances in which shareholder approval is specifically required by law (such as changes to fundamental investment policies) or where a shareholder approval requirement was specifically disclosed in the fund's prospectus, statement of additional information or shareholder report and is otherwise still in effect.

The fund's fundamental investment policies

The fund has adopted the following investment restrictions which may not be changed without the affirmative vote of a "majority of the outstanding voting securities" of the fund (which is defined in the 1940 Act to mean the affirmative vote of the lesser of (1) more than 50% of the outstanding common shares and of the outstanding preferred shares of the fund, each voting as a separate class, or (2) 67% or more of the common shares and of the preferred shares, each voting as a separate class, present at a meeting if more than 50% of the outstanding shares of each class are represented at the meeting in person or by proxy).

Under normal market conditions, the fund invests at least 80% of its total assets in municipal bonds.

Additionally, the fund may not:

1. Issue senior securities, as defined in the 1940 Act, other than shares of beneficial interest with preference rights, except to the extent such issuance might be involved with respect to borrowings described under restriction 2 below or with respect to transactions involving financial futures, options, and other financial instruments.

2. Borrow money in excess of 10% of the value (taken at the lower of cost or current value) of its total assets (not including the amount borrowed) at the time the borrowing is made, and then only from banks as a temporary measure (not for leverage) in situations which might otherwise require the untimely

disposition of portfolio investments or for extraordinary or emergency purposes. Such borrowings will be repaid before any additional investments are purchased.

3. Underwrite securities issued by other persons except to the extent that, in connection with the disposition of its portfolio investments, it may be deemed to be an underwriter under the federal securities laws.

4. Purchase or sell real estate, although it may purchase securities of issuers which deal in real estate, securities which are secured by interests in real estate, and securities representing interests in real estate, and it may acquire and dispose of real estate or interests in real estate acquired through the exercise of its rights as a holder of debt obligations secured by real estate or interests therein.

5. Purchase or sell commodities or commodity contracts, except that the fund may purchase and sell financial futures contracts and options and may enter into foreign exchange contracts and other financial transactions not involving physical commodities.

6. Make loans, except by purchase of debt obligations in which the fund may invest consistent with its investment policies (including without limitation debt obligations issued by other Putnam funds), by entering into repurchase agreements, or by lending its portfolio securities.

7. With respect to 50% of its total assets, invest in the securities of any issuer if, immediately after such investment, more than 5% of the total assets of the fund (taken at current value) would be invested in the securities of such issuer; provided that this limitation does not apply to obligations issued or guaranteed as to interest or principal by the U.S. government or its agencies or instrumentalities.

8. With respect to 50% of its total assets, acquire more than 10% of the outstanding voting securities of any issuer.

9. Purchase securities (other than securities of the U.S. government, its agencies or instrumentalities or tax-exempt securities, except tax-exempt securities backed only by the assets and revenues of non-governmental issuers) if, as a result of such purchase, more than 25% of the fund's total assets would be invested in any one industry.

Terms and definitions

Important terms

Total return shows how the value of the fund's shares changed over time, assuming you held the shares through the entire period and reinvested all distributions in the fund.

Net asset value (NAV) is the value of all your fund's assets, minus any liabilities, divided by the number of outstanding shares.

Market price is the current trading price of one share of the fund. Market prices are set by transactions between buyers and sellers on exchanges such as the New York Stock Exchange.

Fixed income terms

Current rate is the annual rate of return earned from dividends or interest of an investment. Current rate is expressed as a percentage of the price of a security, fund share, or principal investment.

Yield curve is a graph that plots the yields of bonds with equal credit quality against their differing maturity dates, ranging from shortest to longest. It is used as a benchmark for other debt, such as mortgage or bank lending rates.

Comparative indexes

Bloomberg Municipal Bond Index is an unmanaged index of long-term, fixed-rate, investment-grade tax-exempt bonds.

Bloomberg U.S. Aggregate Bond Index is an unmanaged index of U.S. investment-grade fixed-income securities.

ICE BofA (Intercontinental Exchange Bank of America) U.S. 3-Month Treasury Bill Index is an unmanaged index that seeks to measure the performance of U.S. Treasury bills available in the marketplace.

S&P 500^®Index is an unmanaged index of common stock performance.

Indexes assume reinvestment of all distributions and do not account for fees. Securities and performance of a fund and an index will differ. You cannot invest directly in an index.

BLOOMBERG^® is a trademark and service mark of Bloomberg Finance L.P. and its affiliates (collectively "Bloomberg"). Bloomberg or Bloomberg's licensors own all proprietary rights in the Bloomberg Indices. Neither Bloomberg nor Bloomberg's licensors approve or endorse this material, or guarantee the accuracy or completeness of any information herein, or make any warranty, express or implied, as to the results to be obtained therefrom, and to the maximum extent allowed by law, neither shall have any liability or responsibility for injury or damages arising in connection therewith.

ICE Data Indices, LLC ("ICE BofA"), used with permission. ICE BofA permits use of the ICE BofA indices and related data on an "as is" basis; makes no warranties regarding same; does not guarantee the suitability, quality, accuracy, timeliness, and/or completeness of the ICE BofA indices or any data included in, related to, or derived therefrom; assumes no liability in connection with the use of the foregoing; and does not sponsor, endorse, or recommend Putnam Investments, or any of its products or services.

Lipper, a Refinitiv company, is a third-party industry-ranking entity that ranks mutual funds. Its rankings do not reflect sales charges. Lipper rankings are based on total return at net asset value relative to other funds that have similar current investment styles or objectives as determined by Lipper. Lipper may change a fund's category assignment at its discretion. Lipper category averages reflect performance trends for funds within a category.

Other information for shareholders

Important notice regarding share repurchase program

In September 2021, the Trustees of your fund approved the renewal of a share repurchase program that had been in effect since 2005. This renewal allows your fund to repurchase, in the 365 days beginning October 1, 2021, up to 10% of the fund's common shares outstanding as of September 30, 2021.

Important notice regarding delivery of shareholder documents

In accordance with Securities and Exchange Commission (SEC) regulations, Putnam sends a single notice of internet availability, or a single printed copy, of annual and semiannual shareholder reports, prospectuses, and proxy statements to Putnam shareholders who share the same address, unless a shareholder requests otherwise. If you prefer to receive your own copy of these documents, please call Putnam at 1-800-225-1581, and Putnam will begin sending individual copies within 30 days.

Proxy voting

Putnam is committed to managing our mutual funds in the best interests of our shareholders. The Putnam funds' proxy voting guidelines and procedures, as well as information regarding how your fund voted proxies relating to portfolio securities during the 12-month period ended June 30, 2021, are available in the Individual Investors section of putnam.com and on the SEC's website, www.sec.gov. If you have questions about finding forms on the SEC's website, you may call the SEC at 1-800-SEC-0330. You may also obtain the Putnam funds' proxy voting guidelines and procedures at no charge by calling Putnam's Shareholder Services at 1-800-225-1581.

Fund portfolio holdings

The fund will file a complete schedule of its portfolio holdings with the SEC for the first and third quarters of each fiscal year on Form N-PORT within 60 days of the end of such fiscal quarter. Shareholders may obtain the fund's Form N-PORT on the SEC's website at www.sec.gov.

Prior to its use of Form N-PORT, the fund filed its complete schedule of its portfolio holdings with the SEC on Form N-Q, which is available online at www.sec.gov.

Trustee and employee fund ownership

Putnam employees and members of the Board of Trustees place their faith, confidence, and, most importantly, investment dollars in Putnam mutual funds. As of April 30, 2022, Putnam employees had approximately $492,000,000 and the Trustees had approximately $72,000,000 invested in Putnam mutual funds. These amounts include investments by the Trustees' and employees' immediate family members as well as investments through retirement and deferred compensation plans.

Important notice regarding Putnam's privacy policy

In order to conduct business with our shareholders, we must obtain certain personal information such as account holders' names, addresses, Social Security numbers, and dates of birth. Using this information, we are able to maintain accurate records of accounts and transactions.

It is our policy to protect the confidentiality of our shareholder information, whether or not a shareholder currently owns shares of our funds. In particular, it is our policy not to sell information about you or your accounts to outside marketing firms. We have safeguards in place designed to prevent unauthorized access to our computer systems and procedures to protect personal information from unauthorized use.

Under certain circumstances, we must share account information with outside vendors who provide services to us, such as mailings and proxy solicitations. In these cases, the service providers enter into confidentiality agreements with us, and we provide only the information necessary to process transactions and perform other services related to your account. Finally, it is our policy to share account information with your financial representative, if you've listed one on your Putnam account.

Summary of Putnam closed-end funds' amended and restated dividend reinvestment plans

Putnam Managed Municipal Income Trust, Putnam Master Intermediate Income Trust, Putnam Municipal Opportunities Trust and Putnam Premier Income Trust (each, a "Fund" and collectively, the "Funds") each offer a dividend reinvestment plan (each, a "Plan" and collectively, the "Plans"). If you participate in a Plan, all income dividends and capital gain distributions are automatically reinvested in Fund shares by the Fund's agent, Putnam Investor Services, Inc. (the "Agent"). If you are not participating in a Plan, every month you will receive all dividends and other distributions in cash, paid by check and mailed directly to you.

Upon a purchase (or, where applicable, upon registration of transfer on the shareholder records of a Fund) of shares of a Fund by a registered shareholder, each such shareholder will be deemed to have elected to participate in that Fund's Plan. Each such shareholder will have all distributions by a Fund automatically reinvested in additional shares, unless such shareholder elects to terminate participation in a Plan by instructing the Agent to pay future distributions in cash. Shareholders who were not participants in a Plan as of January 31, 2010, will continue to receive distributions in cash but may enroll in a Plan at any time by contacting the Agent.

If you participate in a Fund's Plan, the Agent will automatically reinvest subsequent distributions, and the Agent will send you a confirmation in the mail telling you how many additional shares were issued to your account.

To change your enrollment status or to request additional information about the Plans, you may contact the Agent either in writing, at P.O. Box 8383, Boston, MA 02266-8383, or by telephone at 1-800-225-1581 during normal East Coast business hours.

How you acquire additional shares through a Plan If the market price per share for your Fund's shares (plus estimated brokerage commissions) is greater than or equal to their net asset value per share on the payment date for a distribution, you will be issued shares of the Fund at a value equal to the higher of the net asset value per share on that date or 95% of the market price per share on that date.

If the market price per share for your Fund's shares (plus estimated brokerage commissions) is less than their net asset value per share on the payment date for a distribution, the Agent will buy Fund shares for participating accounts in the open market. The Agent will aggregate open-market purchases on behalf of all participants, and the average price (including brokerage commissions) of all shares purchased by the Agent will be the price per share allocable to each participant. The Agent will generally complete these open-market purchases within five business days following the payment date. If, before the Agent has completed open-market purchases, the market price per share (plus estimated brokerage commissions) rises to exceed the net asset value per share on the payment date, then the purchase price may exceed the net asset value per share, potentially resulting in the acquisition of fewer shares than if the distribution had been paid in newly issued shares.

How to withdraw from a Plan Participants may withdraw from a Fund's Plan at any time by notifying the Agent, either in writing or by telephone. Such withdrawal will be effective immediately if notice is received by the Agent with sufficient time prior to any distribution record date; otherwise, such withdrawal will be effective with respect to any subsequent distribution following notice of withdrawal. There is no penalty for withdrawing from or not participating in a Plan.

Plan administration The Agent will credit all shares acquired for a participant under a Plan to the account in which the participant's common shares are held. Each participant will

be sent reasonably promptly a confirmation by the Agent of each acquisition made for his or her account.

About brokerage fees Each participant pays a proportionate share of any brokerage commissions incurred if the Agent purchases additional shares on the open market, in accordance with the Plans. There are no brokerage charges applied to shares issued directly by the Funds under the Plans.

About taxes and Plan amendments Reinvesting dividend and capital gain distributions in shares of the Funds does not relieve you of tax obligations, which are the same as if you had received cash distributions. The Agent supplies tax information to you and to the IRS annually. Each Fund reserves the right to amend or terminate its Plan upon 30 days' written notice. However, the Agent may assign its rights, and delegate its duties, to a successor agent with the prior consent of a Fund and without prior notice to Plan participants.

If your shares are held in a broker or nominee name If your shares are held in the name of a broker or nominee offering a dividend reinvestment service, consult your broker or nominee to ensure that an appropriate election is made on your behalf. If the broker or nominee holding your shares does not provide a reinvestment service, you may need to register your shares in your own name in order to participate in a Plan.

In the case of record shareholders such as banks, brokers or nominees that hold shares for others who are the beneficial owners of such shares, the Agent will administer the Plan on the basis of the number of shares certified by the record shareholder as representing the total amount registered in such shareholder's name and held for the account of beneficial owners who are to participate in the Plan.

Audited financial statements

These sections of the report, as well as the accompanying Notes, preceded by the Report of Independent Registered Public Accounting Firm, constitute the fund's audited financial statements.

The fund's portfolio lists all the fund's investments and their values as of the last day of the reporting period. Holdings are organized by asset type and industry sector, country, or state to show areas of concentration and diversification.

Statement of assets and liabilities shows how the fund's net assets and share price are determined. All investment and non-investment assets are added together. Any unpaid expenses and other liabilities are subtracted from this total. The result is divided by the number of shares to determine the net asset value per share. (For funds with preferred shares, the amount subtracted from total assets includes the liquidation preference of preferred shares.)

Statement of operations shows the fund's net investment gain or loss. This is done by first adding up all the fund's earnings - from dividends and interest income - and subtracting its operating expenses to determine net investment income (or loss). Then, any net gain or loss the fund realized on the sales of its holdings - as well as any unrealized gains or losses over the period - is added to or subtracted from the net investment result to determine the fund's net gain or loss for the fiscal period.

Statement of changes in net assets shows how the fund's net assets were affected by the fund's net investment gain or loss, by distributions to shareholders, and by changes in the number of the fund's shares. It lists distributions and their sources (net investment income or realized capital gains) over the current reporting period and the most recent fiscal year-end. The distributions listed here may not match the sources listed in the Statement of operations because the distributions are determined on a tax basis and may be paid in a different period from the one in which they were earned.

Statement of cash flows shows changes in the fund's cash balance during the period as results of cash flows from operating and financing activities.

Financial highlights provide an overview of the fund's investment results, per-share distributions, expense ratios, net investment income ratios, and portfolio turnover in one summary table, reflecting the five most recent reporting periods. In a semiannual report, the highlights table also includes the current reporting period.

Report of Independent Registered Public Accounting Firm

To the Board of Trustees and Shareholders of
Putnam Municipal Opportunities Trust:

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities, including the fund's portfolio, of Putnam Municipal Opportunities Trust (the "Fund") as of April 30, 2022, the related statement of operations and cash flows for the year ended April 30, 2022, the statement of changes in net assets for each of the two years in the period ended April 30, 2022, including the related notes, and the financial highlights for each of the five years in the period ended April 30, 2022 (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund as of April 30, 2022, the results of its operations and its cash flows for the year then ended, the changes in its net assets for each of the two years in the period ended April 30, 2022 and the financial highlights for each of the five years in the period ended April 30, 2022 in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Fund's management. Our responsibility is to express an opinion on the Fund's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits of these financial statements in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of April 30, 2022 by correspondence with the custodian, transfer agent and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

PricewaterhouseCoopers LLP
Boston, Massachusetts
June 14, 2022

We have served as the auditor of one or more investment companies in the Putnam Investments family of funds since at least 1957. We have not been able to determine the specific year we began serving as auditor.

Key to holding's abbreviations

Level 1: Valuations based on quoted prices for identical securities in active markets.

Level 2: Valuations based on quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3: Valuations based on inputs that are unobservable and significant to the fair value measurement.