State elections were held in South Australia on 9 and 16 April 1921. All 46 seats in the South Australian House of Assembly were up for election. The incumbent Liberal Union government led by Premier of South Australia Henry Barwell defeated the opposition Australian Labor Party led by Leader of the Opposition John Gunn. Each district elected multiple members, with voters casting multiple votes. The coalition between the National Labor Party and the Liberal Union had collapsed in 1920, and the National Labor Party contested the election as the Progressive Country Party.