Joan Heather Duncan, née Tratch (October 30, 1941 – September 23, 2015[1]) was a pharmacist and politician in Saskatchewan.
She represented Maple Creek from 1978 to 1991 in the Legislative Assembly of Saskatchewan as a Progressive Conservative.
Together they owned and operated Duncan's Drug Store in Maple Creek.
Duncan was first elected to the Saskatchewan Legislature in 1978 and served as a Progressive Conservative MLA for the Maple Creek constituency until 1991.
Duncan and Patricia Anne Smith were the first female Cabinet ministers appointed to Executive Council in Saskatchewan.