Werdum (19-5-1) got off to a slow start, but hit Hunt with a right knee to the face to secure the win in the UFC's debut in Mexico. It was the fifth consecutive victory for the Brazilian fighter.
"I respect Mark Hunt, he hit me hard, but I stayed here a long time in Mexico to win this title, this one is for my family and all of Brazil," Werdum said.
The event was supposed to be a showcase for Cain Velasquez, the Mexican-American champion who has a strong following in Mexico. Instead, the oft-injured Velasquez hurt his right knee and dropped out of his bout against Werdum last month, sending the UFC scrambling for something to show the 21,000 fans who sold out the Arena Cuidad de Mexico in eight hours.
Hunt (10-9-1), a 40-year-old Australian brawler with a history of thrilling fights, got the call from the UFC one month after he stopped Roy Nelson in Japan for his fifth win in seven fights, losing only to former UFC champion Junior Dos Santos in that stretch.
But Hunt was unable to continue his positive stretch.
"I didn't see that one coming," Hunt said of the knee that ended the fight.
Velasquez was part of a sold-out crowd at the raucous Arena Ciudad de Mexico. The Mexican fans, who had waited for years for the UFC to come to their country, sang the Cielito Lindo, a tradition for any big event, and chanted "oles."
Prior to the main event, rising Mexican-American welterweight Kelvin Gastelum (11-0) took care of veteran title contender Jake Ellenberger (29-9) by submission in the first round.
"This is the biggest victory of my career, I*m so happy to get here with all of you guys," an emotional Gastelum said in Spanish. "Viva Mexico, thanks for everything."
In the undercard fights, Mexico City*s Augusto Montano had a strong UFC debut by defeating Chris Heatherly (8-3-0) by TKO in the first round of their welterweight fight. Hector Garcia defeated Edgar Garcia by tapout in the first round, also in the welterweight division. Featherweight Ricardo Lamas also won.