Mayor Ron Nirenberg won re-election in a 14-candidate nonpartisan general election for mayor in San Antonio, Texas, on May 1, 2021. Nirenberg received 61.9% of the vote. 2019 challenger Greg Brockhouse received 31.5% of the vote. No other candidate received more than 2% of the vote.

In the lead-up to the election, media coverage focused on Nirenberg, Brockhouse (who previously ran against Nirenberg in 2019 and lost by 2.2% in the runoff election), and Denise Gutierrez-Homer. Brockhouse and Gutierrez-Homer both disagreed with Nirenberg’s response to the pandemic, including mask mandates and business restrictions. Proposition B, a ballot measure repealing local authority for collective bargaining with the San Antonio Police Officers Association to negotiate wages, healthcare, leave, and other policies, was also an issue in the race. Nirenberg said that the issue was best left to voters, while Brockhouse and Gutierrez-Homer both opposed it.

The mayor is a member of the city council. He or she presides over council meetings and official city ceremonies. The mayor also represents the city on the state, national and international levels.