Justin Gaethje produced the best performance of his career to finish Tony Ferguson and win the UFC interim lightweight title at UFC 249.
The event was held behind closed doors in Jacksonville, Florida, after the global coronavirus pandemic forced several changes to the card and venue.
Undisputed champion Khabib Nurmagomedov was originally set to face Ferguson on 18 April in Brooklyn, but the coronavirus outbreak forced the event to be moved, and the UFC's attempt to hold the show on tribal land in Lemoore, California, was halted after broadcast partner ESPN and parent company Disney intervened.
Eventually, it was moved to the VyStar Veterans Memorial Arena in Jacksonville, where it became the first major US sporting event to take place since March.
More than 77,000 people have now died with Covid-19 in the United States and there are 1.2 million confirmed cases - both figures the highest in the world.
Brazilian middleweight Jacare Souza and his two cornermen tested positive for coronavirus on the eve of the event and were withdrawn.
On the night there were strict health and safety protocols in place. The referees, commentators and event staff wore face masks and only one cornerman per fighter was allowed into the cage between rounds.
Without the crowd, fighters said they could hear the commentators.
Heavyweight Greg Hardy said he was able to take the advice of commentator Daniel Cormier as he beat Yorgan de Castro.
"Thank God for not having the crowd," Hardy said in his post-fight interview. "Shout out to DC. I heard him tell me to check him, so I started trying to check him. Game changer."
Carla Esparza, who beat Michelle Waterson, said she heard Cormier's criticism of her and changed her strategy during the fight.
Fans watching at home commented on how noisy and "terrifying" the punches sounded in an empty arena.
'I'll wait for the real one' - Gaethje after victory
While the night saw a host of thrilling fights, all eyes were on the main event between Americans Gaethje and Ferguson, with the winner set to move on to Nurmagomedov later this year.
Gaethje, 31, stepped in to face Ferguson at the start of April, and took his chance with a calm, composed display to win the belt and set himself up for a shot at the Russian champion.
Gaethje started superbly and settled into his work in the first two rounds, but was dropped by a huge Ferguson uppercut in the final seconds of round two.
Undeterred, Gaethje continued to connect with powerful shots as Ferguson maintained his forward pressure and put the former interim champion on wobbly legs with a big punch early in round four.
By that point, Gaethje's solid, accurate punches had started to take their toll on a bloodied and bruised Ferguson, and when a stiff jab forced Ferguson backwards, midway through the fifth and final round, referee Herb Dean stepped in to end the contest.
It saw Gaethje awarded the interim lightweight belt, but he waved it away, saying he's waiting for the "real thing", as he laid out his wish to take on Nurmagomedov in a title unification bout in his next outing.
"Khabib is the best in the world," he said.
"I've been working since I was four for challenges like this, and I'm happy to represent the United States of America against Dagestan (Khabib's home region), or Russia's best. He's 28-0, and there's no other challenge I want right now. I want to fight him."
Cejudo retains his belt, then retires
The night's co-main event saw 2008 Olympic wrestling gold medallist Henry Cejudo successfully defend his UFC bantamweight title against former champion Dominick Cruz, then make a surprise announcement as he confirmed his retirement from the sport.
The 33-year-old transitioned to mixed martial arts in 2013. His skills eventually saw him make it to the UFC, where he dethroned all-time great Demetrious 'Mighty Mouse' Johnson to win the UFC flyweight title.
Cejudo then moved up to 135 pounds and came from behind to defeat Marlon Moraes to capture the bantamweight title and become a UFC 'champ champ', but eventually relinquished the flyweight belt to focus on life at his new weight class.
His first title defence came against former two-time champion Cruz, who was returning from a three-and-a-half-year lay-off in a bid to reclaim the title.
It was Cejudo whose skills prevailed on the night as he countered Cruz's unorthodox footwork with powerful leg kicks and, after an accidental clash of heads forced the fight into a brief pause, he connected with a huge knee that dropped Cruz to the mat.
With the former champion looking to scramble back to his feet, Cejudo swarmed his downed opponent and landed 11 unanswered shots to force referee Keith Petersen to step in and wave off the fight with just two seconds remaining in the round.
After his victory, Cejudo said: "I'm retiring tonight. I'm 33 years old, I'm happy with my career. Uncle Dana (White, UFC president), I want to say thank you for everything, you're the man. Everybody here, thank you so much."