Denys Berinchyk has stopped Emanuel Navarrete's bid to become a four-weight world champion with a split-decision victory (116-112, 115-113, 113-115) in San Diego.
The result capped off an unforgettable day for Ukrainian boxing after Oleksandr Usyk had earlier captured the undisputed heavyweight title with a a split-decision victory of his own over Tyson Fury in Riyadh.
All four belts at lightweight are now accounted for after Berinchyk's countryman Vasiliy Lomachenko picked up the IBF strap last week, joining Shakur Stevenon (WBC) and Gervonta Davis (WBA) as champions at 135-pounds.
MORE: Usyk claims undisputed title in classic with Fury
After his victory, Berinchyk listed three possible opponents for his next fight.
"Shakur Stevenson, Keyshawn Davis, maybe [Raymond] Muratalla, I don't know, I don't give a f---," he said.
Berinchyk's activity, movement and ring generalship were features of the bout, which reflected the unique and awkward styles of the two combatants.
Despite winning his first world title down at 122-pounds, Navarrete's size advantage was clear from the outset, although the switch-hitting Berinchyk had no hesitation trading with him, finding some success in the first round on the back of some busy feet.
Navarrete's unorthodox style proved effective in round two, landing some hard shots with straight right hands and looping lefts.
A right hook in the third found the target for Berinchyk before Navarrete fired back with an uppercut of his own as the fight settled into an awkward and unpredictable rhythm.
The pair exchanged wildly in the fourth, both fighters using every inch of the ring to set up attacks and get clear of the heat coming back the other way but a left uppercut did land clean to hurt Berinchyk.
Over the next few rounds, they seemed to take turns firing combinations off, venturing into the sloppy range at times as they threw and defended while on the move.
Having taken some shots from Navarrete, Berinchyk's confidence grew into the second half of the fight, bettering the output of the notoriously busy three-weight world champion.
Navarrete came out aggressively in the 10th and an accidental head butt had him in clear discomfort.
Upon the restart, Berinchyk was happy to trade and may have even squared the majority of the exchanges.
The 11th was full of action and Navarrete landed some hard shots, the likes of which might have dropped his previous opponents in the lighter weight classes, but Berinchyk stood up to them well.
If the fight could be wrapped up in three minutes, the 12th and final round would be an appropriate summary, as both fighters danced around the ring throwing plenty of punches, catching just as much air as they did body and head.
The result sees Berinchyk improve to 19-0, while Navarrete slips to 38-2-1, having tasted defeat for the first time in over a decade.
In the co-main event, Brian Norman won the interim WBO welterweight world title after a bloody war with Giovani Santillan.
Norman had made a complete mess of Santillan's nose, eventually putting him down twice in the 10th round to secure the knockout victory, courtesy of uppercuts with each hand.
Santillan tasted defeat for the first time in 33 fights, while Norman improves to 26-0 as a professional.
Emanuel Navarrete vs. Denys Berinchyk fight card results
- Denys Berinchyk def. Emanuel Navarrete via SD12 for vacant WBO lightweight title
- Brian Norman def. Giovani Santillan via KO10 for the interim WBO welterweight title
- Richard Torrez Jr. def. Brandon Moore via TKO5; heavyweight
- Jonny Mansour def. Anel Dudo via UD4; lightweight
- Emiliano Vargas def. Angel Varela Urena via TKO6; lightweight
- Alan Garcia def. Wilfredo Flores via UD8; lightweight
- Jonathan Lopez def. Edgar Ortega via TKO8; super featherweight
- Art Barrera Jr. def. Levy Josue Garcia via UD4; super lightweight