John Jacob Weinzweig (March 11, 1913 – August 24, 2006) was a composer, teacher, and advocate of contemporary Canadian concert music.

Born in Toronto, Weinzweig went to Harbord Collegiate Institute, then studied music at the University of Toronto. 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 the University of Toronto. In the previous year he had co-founded the Canadian League of Composers, and he was actively involved in several other organizations 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.

In 2004, Weinzweig was the recipient of the inaugural Lifetime Achievement Award at the annual SOCAN Awards in Toronto.