Peter Duncan (born 1 January 1945) is an Australian Labor Party politician and one of the relatively few members of parliament to have served not only in both a state and national parliament but also as a minister in both cases. Peter Duncan was born in Melbourne and went to the University of Adelaide, where he studied law and was co-editor of the student newspaper On Dit in 1968. He was elected to the South Australian House of Assembly from the electorate of Elizabeth in the 1973 South Australian election, when he was 28.