The Folsom Street Fair (FSF) is an annual BDSM and leather subculture street fair held on the last Sunday in September and caps San Francisco's "Leather Pride Week". The Folsom Street Fair, sometimes simply referred to as "Folsom", takes place on Folsom Street between 7th and 12th Streets, in San Francisco's South of Market district.

The event started in 1984 and is California's third largest spectator event and the world's largest leather event and showcase for BDSM products and culture.[1] It has grown as a non-profit charity, and local and national non-profits benefit with all donations at the gates going to charity groups as well as numerous fundraising schemes within the festival including games, beverage booths and even spanking for donations to capitalize on the adult-themed exhibitionism.

The coordination agency, Folsom Street Events (FSE) is a registered charity and has also started similar events in Canada and Germany. In San Francisco they also manage Dore Alley Fair and special events like the "Folsom Street Fair Formal Leather Gala" with Joan Rivers which celebrated the 25th anniversary, and their annual circuit party "Magnitude" which has a leather subculture focus.