Sinclair Alexander Whittaker (1888 – July 10, 1974) was a merchant and political figure in Saskatchewan. He represented Moose Jaw County from 1929 to 1934 in the Legislative Assembly of Saskatchewan as a Conservative.He was born in Port Perry, Ontario and, in 1910, moved to Briercrest, Saskatchewan. He operated a small chain of general stores in the province. Sinclair helped found the Briercrest Bible Institute and served as chairman of the board for the institute.