A by-election was held for the South Australian House of Assembly seat of Mitcham on 8 May 1982. The by-election was triggered by the resignation of former state Democrats MHA Robin Millhouse. The Liberal Party was expected to win the seat, but Democrats candidate Heather Southcott was heavily favoured by Labor party preferences, and was a surprise winner. The Liberals won the seat six months later at the 1982 state election.