The 2021 St. Petersburg, Florida, mayoral election was held on August 24, 2021, with a runoff on November 2 because no candidate received more than 50% of the vote in the first round. It elected the mayor of St. Petersburg, Florida. Incumbent Democratic mayor Rick Kriseman was term-limited and could not seek a third term in office. Municipal elections in St. Petersburg are officially nonpartisan. Former Pinellas County commissioner Ken Welch easily defeated city councilor Robert Blackmon in the runoff. Candidates eliminated in the first round included city councilor Darden Rice, former state representative Wengay Newton, and restaurateur Pete Boland. Welch took office in January 2022, becoming the first black mayor of St. Petersburg.
Endorsements in bold were made after the general election.