Canada High: Mikaela Mayer Wins Unified Super Welterweight Crown Mayer is now a three-weight world champion MONTREAL, Canada (Oct. 30, 2025) — Mikaela Mayer traveled to enemy territory and is coming back to America as a three-belt world champion. Mayer defeated Canada’s Mary Spencer via one-sided unanimous (100-90 and 98-92 2x) to capture the WBA, WBC, and