John Stewart McDiarmid (December 25, 1882 – June 7, 1965) was a Manitoba politician. He held senior ministerial positions in the governments of John Bracken, Stuart Garson and Douglas Campbell, and served as the province's 14th Lieutenant Governor between 1953 and 1960. On May 27, 1932, McDiarmid was appointed and in the government of provincial Premier John Bracken. This occurred after negotiations in which the provincial Liberal party merged with Bracken's governing Progressives; McDiarmid received one of the cabinet positions designated for the Liberal Party.