Gabe Mastromatteo (born April 27, 2002) is a Canadian competitive swimmer who specializes in the breastroke.

[1] In 2017, Mastromatteo was part of the gold medal team that won the 4x100 mixed medley at the 2017 World Junior Swimming Championships.

[2] As part of the 2021 Canadian Olympic swimming trials in Toronto, Mastromatteo won the 100 m breaststroke race.

[3][4][5] He placed thirty-eighth in the heats of the 100 m breaststroke, his lone individual event.

He stated his main focus was on the 4x100 m medley relay, where the Canadian men's team made the final and placed seventh, with Mastromatteo swimming a new personal best relay time on the breaststroke leg.