Brandon Johnson defeated Paul Vallas in the runoff election for mayor of Chicago, Illinois, on April 4, 2023. Johnson received 51.4% of the vote and Vallas received 48.6%. They advanced from a field of nine candidates in the Feb. 28 general election.

Johnson was elected to the Cook County Board of Commissioners as a Democrat in 2018. He was a teacher with Chicago Public Schools and an organizer with the Chicago Teachers Union (CTU). The CTU endorsed Johnson. He received 20.3% of the vote in the general election.

Vallas was the 2014 Democratic nominee for lieutenant governor. He worked as chief administrative officer at Chicago State University and was the CEO of Chicago Public Schools. The Chicago Fraternal Order of Police endorsed Vallas. He received 33.7% of the vote in the general election.

Incumbent Lori Lightfoot finished third in the general election with 17.1% of the vote and did not advance to the runoff. Lightfoot, who was elected in 2019, was the first incumbent Chicago mayor to lose a re-election bid since 1983 when Jane Byrne lost her primary.

Although elections are officially nonpartisan, candidates are typically affiliated with one of the major political parties. Johnson and Vallas are both Democrats. The last Republican mayor of Chicago, William Thompson, left office in 1931.