John (Jacob) Weinzweig was a Canadian composer of classical music. Born in Toronto, Weinzweig went to Harbord Collegiate Institute, and studied music at the university. In 1937, he left for the United States to study under Bernard Rogers.

During the Second World War, he began composing film music, and in 1952 he became a professor at his old university in Toronto. In the previous year he had co-founded the Canadian League of Composers, and he was actively involved in several other organisations representing musicians and composers. In 1974, he was made an Officer of the Order of Canada. In 1988, he was awarded the Order of Ontario.