Augustus Garrett (1801 – November 30, 1848) twice served as Mayor of Chicago, Illinois (1843–1844, 1845–1846) for the Democratic Party.
Garrett married Eliza Clark in 1825 and moved to Chicago from New York in 1834. He had a small auction house near the Chicago River and by the following year had formed a partnership with the Brown Brothers, which allowed him to become a leading land speculator and auctioneer. By October 1836, he had sales of more than $1.8 million.
Elected mayor in 1843, he won re-election in 1844 only to have the election invalidated based on charges of "illegal proceedings and fraud." Garrett ran in a second election that year, losing to Alson Sherman. During his terms in office, Garrett pushed to have the first brick school in Chicago, Dearborn School, turned into either a warehouse or an insane asylum, believing that the building was too large for use as a school.
Following his death, Eliza established the Garrett Bible Institute, now Garrett-Evangelical Theological Seminary, in nearby Evanston, Illinois.