Sinclair Alexander Whittaker (1888 – July 10, 1974[1]) 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.
He also was chairman of the Retail Merchants Association of Saskatchewan.