David Lewis (born Losz), CC, (June 23, or October 1909 -May 23, 1981) was a Russian-born Canadian labour lawyer and social democratic politician. He was national secretary of the Co-operative Commonwealth Federation (CCF) from 1936 to 1950, and was one of the key architects of the New Democratic Party (NDP) in 1961. He was the NDP's national leader from 1971 to 1975.