Sidney Earle Smith PC QC (9 March 1897 – 17 March 1959) was an academic and Canada's Secretary of State for External Affairs in the government of Prime Minister John Diefenbaker.

Born and raised on Nova Scotia's Port Hood Island, Smith grew up speaking both English and Gaelic.

He remained in that role for twelve years, overseeing a major period of the university's expansion.

After Diefenbaker won a surprise minority government in 1957, Smith was appointed as Secretary of State for External Affairs.

Sidney Smith Hall, the central building of the Faculty of Arts and Science at the University of Toronto, is named after him.