Supplemental Prospectus (Form 424B3)

Filed pursuant to Rule 424(b)(3)
File No. 333-227968

EATON VANCE SENIOR INCOME TRUST
Supplement to Prospectusdated October 21, 2021 and Prospectus Supplement dated October 21, 2021

The following replaces any references, contained either in the Prospectus or the Prospectus Supplement, with respect to the Fund's: (i) last reported sale price; (ii) net asset value ("NAV") per Common Share; (iii) percentage premium to NAV per Common Share; (iv) number of Common Shares outstanding; and (v) net assets.

On May 24, 2022, the last reported sale price, NAV per Common Share and percentage premium to NAV per Common Share, were $5.62, $6.29 and (10.65)%, respectively. As of May 24, 2022, we had 17,538,858 Common Shares outstanding and net assets of approximately $110,260,250.

The following replaces the last sentence in the first paragraph under "Use of Proceeds" in the Prospectus Supplement:

Assuming the sale of all of the Common Shares offered under this Prospectus Supplement and the accompanying Prospectus, at the last reported sale price of $5.62 per share for our Common Shares on the NYSE as of May 24, 2022, we estimate that the net proceeds of this offering will be approximately $10,229,464 after deducting the estimated sales load and the estimated offering expenses payable by the Fund.