Mikaela Mayer outpointed Mary Spencer in Canada to become a unified light-middleweight and a three-division world champion.
The 35-year-old American produced a dominant performance at the Montreal Casino, outboxing the hometown favourite over 10 rounds.
Judges scored the contest 100-90, 98-92 and 98-92 as Mayer claimed the WBA crown and the vacant WBC and WBO belts following trailblazer Cecilia Braekhus’ retirement.
“I’ve won a WBO before but I’ve never had the WBA or WBC put around my waist, so this is extra special,” Mayer said.
Mayer, who is also the reigning WBO champion at welterweight, won her first world title at super-featherweight. Her record now stands at 22 wins and two defeats.
The Californian quickly settled into her rhythm behind a sharp jab, varying her attacks to head and body.
Despite giving up two inches in height to the 5ft 11in Spencer, she controlled the range and tempo throughout.
Spencer, 40, enjoyed brief success in the fourth round when a pair of right hands connected, but Mayer reasserted herself, closing the eighth with four powerful hooks and a wide points victory looked inevitable.
Spencer was bloodied and marked under both eyes at the final bell as the Canadian suffered a third defeat in 13 bouts.
“She’s a strong, solid opponent. Props to her, she didn’t have to take this fight,” Mayer said. “She took a big risk taking on a fighter like me. I always come forward and put on tough fights.”
Mayer reaffirmed her life-long goal of becoming an undisputed champion after a second consecutive win over Briton Sandy Ryan earlier this year.
She had hoped to face Wales’ Lauren Price, the WBC welterweight champion, in an undisputed fight.
That bout fell through largely because of promotional and broadcast issues.
If a fight with Price – who is expected to be back in action in the UK in December – does not materialise next for Mayer, she could pursue undisputed status at light-middleweight against IBF champion Oshae Jones.
“The most important thing is that I have options,” Mayer said.
“I’d love to do both – go back down to 147lb for undisputed, then come back up and defend at 154lb.”
A potential super-fight could also be on the cards against Claressa Shields, the self-proclaimed ‘Greatest Woman of All Time’ and undisputed three-weight world champion, who currently holds titles at heavyweight.
American Shields, currently a free agent, is attracting interest from several promoters, including Most Valuable Promotions, co-founded by Jake Paul and Nakisa Bidarian.
If Shields were to move down to super-middleweight, Mayer – despite it not being a natural weight – has said she would gladly meet her there.