Saul ‘Canelo’ Alvarez unified the middleweight division with a points victory over Daniel Jacobs in Las Vegas.
The Mexican – now beaten just once in 55 fights – took Jacobs’ IBF belt to add to his own WBC and WBA titles.
Judges scored the fight 115-113, 115-113, 116-112 in Canelo’s favour after 12 rounds.
And the scorecard reflected Canelo’s improved defence and counterattacking skills in his return to 160lb.
The 28-year-old became a three-weight world champion when moving up a division to face England’s Rocky Fielding last year, but he returned to middleweight to face New Yorker Jacobs, 32, in what was his second bout of a reported £278m deal with streaming service DAZN.
Boxing fans will now be hoping to see Canelo face another American – WBO middleweight champion Demetrius Andrade – to become the undisputed middleweight king.
“Nobody in Mexico has ever done that, won all four belts in one division, so that’s my motivation,” Alvarez said, before the Jacobs fight.
Jacobs – known as the ‘Miracle Man’ after returning to the ring and becoming a champion following cancer – now has three defeats from his 38 fights.