Katie Taylor lifted all four world lightweight titles with a narrow victory over Delfine Persoon at Madison Square Garden in New York.
In her 14th fight as a professional, she added the WBC title to those she already possessed from the IBF, WBA and WBO to become only the seventh fighter of the four-belt era to become an undisputed world champion, as well as only the third woman.
The 32-year-old from Ireland had to survive her toughest rounds as a professional as Persoon, who had a significant size advantage, threatened to force a stoppage in the 10th and final round, but having reached the final bell she was awarded a majority decision via scores 95-95, 96-94 and 96-94.
As an outstanding amateur, Taylor won five world titles, six European titles and Olympic gold with Ireland at London 2012, but her achievements as a professional may have surpassed even that remarkable success.
The key to her victory was perhaps demonstrated as early as the opening round when the rivals - fighting at a remarkably high pace throughout their two-minute rounds - immediately began to trade as the classier Taylor landed with a quick combination that Persoon struggled to resist.
Their furious exchanges not only continued, and suggested Persoon was stronger and desperate to physically impose herself on her more decorated opponent, but gave the Belgian her greatest chance of success, allowing her to hurt Taylor with occasional big right hands.
In the fifth, Taylor then invited Persoon to continue to trade, but it was at that point that victory threatened to become more routine as her opponent tired having struggled to secure the knockout and increasingly lost her form.
While Taylor's pace also slowed, she did so from a position of comfort and began to tee off on her 34-year-old rival, but she just as quickly found herself at risk again in the seventh and eighth, when she took further flush right hands.
Taylor slipped to the canvas amid an assault in the ninth, by when she was also clearly tiring, took another right and naively fought back instead of protecting herself, and struggled with the physicality forced by an opponent with a by-then severely swollen left eye and forehead.
Another big right hurt Taylor again in the 10th, and as she tired further and barely defended herself she was at risk of being stopped.
In reaching the final bell, again under attack, her demeanour suggested she believed she had lost, but she was confirmed as the undisputed lightweight champion, an achievement she considers the "pinnacle" and surpasses all she has previously achieved.
Bloodied and bruised, Persoon almost instantly then left the ring in tears, having clearly believed she should have won.