Flagg is a surname. Notable people with the surname include:
Abner S. Flagg (1851-1923), American politician
Amy Flagg (1893-1965), British historian
Ann Flagg (1924–1970), African-American playwright, stage actress and drama teacher Azariah C. Flagg, (1790–1873), American politician Edmund Flagg (1815–1890), American writer, lawyer, and diplomat Ella Flagg Young (1845–1918), American educator Ernest Flagg (1857–1947), American architect Fannie Flagg (born 1944), American author George Whiting Flagg (1816–1897), American painter Henry Collins Flagg (1792–1863), American lawyer, newspaper editor, and politician James Montgomery Flagg (1877–1960), American artist Jared Bradley Flagg (died 1899), American artist Norman G. Flagg (1867–1948), American politician Ray Dennis Steckler or Cash Flagg (1938–2009), American film director Russell de Gree Flagg (1892–1980), American luthier Willard Cutting Flagg (1867–1948), American politician Wilson Flagg (1938–2001), American admiral
Fictional characters: General Flagg, two characters in the G.I. Joe universe Harry Flagg, a character in the British soap opera Coronation Street Randall Flagg, a villain in several Stephen King novels Sam Flagg, a character in the TV series M*A*S*H Brick Flagg, a character in the animated series Kim Possible