Sean McMahon (born 18 June 1994) is an Australian rugby union player who currently plays as a flanker for the Melbourne Rebels in Super Rugby.
McMahon was born and raised in Queensland and took his first steps in senior rugby with GPS in the Brisbane Premier Grade Championship. He played in the side which was runner-up in the 2013 competition and featured alongside future Rebels team-mates Colby Faingaa and Bryce Hegarty. McMahon's displays saw him named as a member of the Melbourne Rebels extended playing squad for the 2014 Super Rugby season. He was surprisingly named in the number 6 jersey for the Rebels season opener against the Cheetahs at AAMI Park on 28 February 2014. McMahon played the whole 80 minutes in a 35-14 victory for the home side.