Joshua Van delivered a striking masterclass to retain his UFC flyweight championship, defeating Alexandre Pantoja by unanimous decision at UFC 331 in Los Angeles on Saturday night.

The 24-year-old from Myanmar, the first UFC champion from his country, secured scores of 49-46, 49-47, and 50-45 from the judges, cementing his reign atop the 125-pound (56.7 kg) division.

The rematch carried significant weight. In their first meeting in December last year, Pantoja suffered an accidental elbow dislocation just 26 seconds into the fight, leaving Van as champion without a definitive victory over the Brazilian, who had previously held the title for at least two years.

Van had since defended the belt against Tatsuro Taira in May, but the question of who was the division's best fighter lingered until Saturday.

"A lot of people said that was an accidental win ... well, doubt me now," Van said after the fight, which extended his professional MMA record to 18 wins and two losses.

Pantoja came out aggressively in the first round, taking Van down and landing heavy punches and knees before Van responded with a sharp elbow. Between rounds, Van's corner urged a more disciplined approach. "You're too good to brawl with this guy," his coaches told him.

Van adjusted. He peppered Pantoja with left-handed jabs in the second round and rocked the Brazilian with a fluid combination in the third. Pantoja regained control in the fourth, taking Van down again but failing to secure a submission.

In the fifth and final round, Van stalked his opponent and dropped him with an overhand right, sealing the victory on the judges' scorecards.

In the co-main event, Armenian lightweight contender Arman Tsarukyan extended his winning streak to six fights with a first-round knockout of Mauricio Ruffy. Tsarukyan pinned Ruffy to the cage, rocked him with a left elbow, and finished him with a right elbow with four seconds remaining in the round.

"I knew my time would come, so I was patient," Tsarukyan said, calling for a title fight against champion Justin Gaethje.

In featherweight action, former four-time, two-division Bellator champion Patricio Pitbull earned his first UFC stoppage win, defeating South Korea's Dooho Choi by TKO at three minutes and 28 seconds of the opening round. Pitbull, who holds a professional MMA record of 38-9, overwhelmed Choi with high-volume striking before landing a decisive right hand that prompted the referee to stop the contest. The win snapped a three-fight finishing streak for Choi, who has competed in the UFC since 2014.

In one of the night's most dramatic moments, Sean Sharaf stopped Gable Steveson in just 12 seconds in a heavyweight bout, marking the third-fastest knockout in UFC heavyweight history. Steveson had entered as a heavy betting favourite, but Sharaf caught him immediately in the opening exchange and unleashed a rapid flurry of strikes that forced a near-instant stoppage.

A visibly frustrated Steveson left the Octagon before Sharaf's hand was officially raised, while Sharaf celebrated in front of an electric crowd.