Mary Spencer (born December 12, 1984) is a Canadian professional boxer who as an amateur won three World Championships and a Pan American Games gold medal.

[5] Considered a medal favourite at the London 2012 Summer Olympics, which were the first Games to include women's boxing,[6] Spencer received a bye into the quarter-finals where she lost to China's Li Jinzi who she had beaten in the world championship final two years earlier.

[8][9] Next she took on Belgian boxer Femke Hermans for the vacant IBO female super-welterweight World title losing the bout in Shawnigan, Quebec, Canada, on 16 December 2022 by unanimous decision.

[11] Spencer snapped her losing streak with a win over Sonya Dreiling on 25 January 2024, taking victory via retirement when her American opponent failed to answer the bell at the start of round two.

[12][13] On September 5, 2024 in Montreal, Quebec, Canada, Spencer defeated Naomi Mannes by unanimous decision to win the interim WBA super welterweight title.