INGLEWOOD, Calif. — Amanda Nunes knocked out Cris "Cyborg" Justino 51 seconds into the first round at UFC 232 on Saturday night, ending the featherweight champion's 13-year unbeaten run with one of the most surprising victories in mixed martial arts history.

Nunes, the UFC's bantamweight champion, moved up 10 pounds to challenge Justino (20-2), widely considered the world's greatest female fighter. Nunes became the third fighter in UFC history to hold two title belts simultaneously, joining Conor McGregor and Daniel Cormier.

Nunes (17-4) was thought to be an undersized underdog, but she seized her second title belt by overwhelming her fellow Brazilian in the penultimate bout of the show headlined by former light heavyweight champion Jon Jones' return against Alexander Gustafsson for the 205-pound title.

Nunes buckled Justino's knees in the opening seconds, and she quickly pounced. Nunes eventually knocked down Justino twice, and she ended the fight spectacularly with an overhand right to the ear, putting Justino face-down on the canvas.

Nunes also knocked out Ronda Rousey in less than a minute two years ago.

Just six days after the UFC moved the entire show from Las Vegas to the famous Forum south of downtown Los Angeles, a capacity crowd watched another groundbreaking achievement by Nunes, the ferocious brawler who calls herself "The Lioness."

Nunes' punching power is often too much for her male sparring partners, and she carved up the formidable Justino with astonishing ease despite a size disadvantage. Justino had won 20 consecutive fights since her MMA debut in 2005, and she had dominated since the inception of the UFC's 145-pound division, which was created largely as a showcase for her talent.

The UFC made the extraordinary decision to move its show 280 miles to California to keep Jones on the card. The former champion recently tested positive for low levels of a banned steroid, but California regulatory officials didn't consider the result serious enough to keep the long-troubled star out of the octagon, while Nevada's commission did.

Australian featherweight prospect Alexander Volkanovski (19-1) won his 16th straight bout in the PPV opener, stopping veteran Chad Mendes with right hands in the second round of a back-and-forth bout. Michael Chiesa also won his welterweight debut with a second-round submission of former champ Carlos Condit, who lost his fifth straight fight.

Former UFC lightweight champion BJ Penn tapped out for the first time in his MMA career, losing to Brazilian jiu-jitsu whiz Ryan Hall on a heel hook in the first round. Penn (16-13-2), an MMA pioneer who turned 40 this month, is 0-6-1 in his last seven fights since 2010.