Harry Pulliam Cain, was a United States Senator from Washington who served as a Republican from 1946 to 1953.

Prior to his term in the Senate, he had served as the progressive Mayor of Tacoma, Pierce County, Washington. Following his Senate term he was widely recognized as a defender of the civil liberties of individuals accused of being security risks during the Eisenhower Administration and as a community activist and moderate Republican until his death in 1979.