Justin Duff (born May 10, 1988) is a former Canadian professional volleyball player. He was a member of Canada men's national volleyball team, a bronze medalist of NORCECA Championship (2011, 2013).
In July 2016, he was named to Canada's 2016 Olympic team.
In 2014 he signed a contract with Transfer Bydgoszcz. After one season in Portuguese club Benfica Lisbon and one season in Greek Olympiacos Piraeus, he decided to come back to Poland and join Espadon Szczecin team.