LAS VEGAS — Brock Lesnar defended his heavyweight title in his uniquely brutish style at UFC 100 tonight, capping the sport's landmark weekend with a second-round stoppage of Frank Mir.

Georges St-Pierre defended his welterweight title with a showcase of his inimitably well-rounded mixed martial arts skills in an unanimous decision over Thiago Alves, while Dan Henderson knocked out Michael Bisping with a single punch in a middleweight upset as the UFC rolled its odometer into triple digits on a celebratory night for the proliferating sport.

Lesnar (4-1) ended the main event with a relentless series of right hands into the face of Mir, who handed Lesnar his only loss nearly 18 months ago.

Lesnar, a hulking former pro wrestler with a mercurial temperament, then taunted his opponent while Mir was rising from the ground. He added a two-handed obscene gesture to the booing sellout crowd at the Mandalay Bay Events Center, putting an entertaining but unflattering end on the highest-profile show in the sport's history.

There were no theatrics or poor sportsmanship from St-Pierre, the classy Canadian star considered the UFC's pound-for-pound best. He was the superior fighter from the start, winning every round on every scorecard while steadily punishing his Brazilian opponent with punches, kicks and repeated takedowns in his third title defense.

Nearly 16 years after MMA pioneer Royce Gracie won three fights in one night to triumph at UFC 1 in Denver, the sport reached a centennial of sorts before a frenzied sellout crowd in the UFC's hometown. The arena was packed well before the main bouts, including some fans who apparently paid more than $40,000 online for resold tickets.

The league has grown from a bit player in a fringe pastime to an estimated $1 billion company, and the weekend's festivities reflected its success despite the widespread skepticism it still faces from other sports fans and some states' lawmakers.

The 100th showcase was broadcast live in 75 countries, and thousands of fans without tickets for the event packed into closed-circuit shows all along the Strip. Tens of thousands attended the first UFC Fan Expo, immersing themselves in the lifestyle built around the sport.

Lesnar, who turns 32 on Sunday, again moved upward in the eclectic trajectory of a former college wrestler who performed in the WWE and briefly suited up for the Minnesota Vikings before embarking on an MMA career just over three years ago.

Mir (12-4) beat Lesnar with a knee bar at UFC 81, forcing Lesnar to tap out 90 seconds into his second UFC fight. Lesnar, whose name recognition and menacing approach earned him lightning-quick shots at the sport's biggest prizes, recovered by beating Heath Herring and then stopping Randy Couture last November to claim the heavyweight belt.

Lesnar used his 265 pounds to take position on top of Mir early, and Lesnar stayed on top throughout a dull first round, throwing punches that mostly did little. Mir made a bit of headway in the second, but was trapped against the octagon by Lesnar, who kept throwing right hands until Mir's defense wilted.

"Keep booing! Keep booing!" Lesnar yelled to the largely unsympathetic crowd.

After dominating the first 14 minutes with several takedowns, St-Pierre (19-2) knocked Alves onto his back with a punch late in the third. But St-Pierre also injured his groin in the third, and Alves (22-5) managed to gain position for the only time in the fight.

St-Pierre escaped and nearly finished it with a rear naked choke on Alves, who lost for the first time in eight fights.

"When I was on my back, he pushed my leg down," St. Pierre said. "It could have been a very bad night for me."

In the undercard showdown between the veteran fighters who served as coaches on the past season of the UFC's popular television show, Henderson (25-7) flattened Bisping with a spectacular right hand in the second round.

Henderson, a Californian who traded verbal barbs with Manchester native Bisping over the past several months, pursued Bisping (18-2) around the octagon during a largely stand-up fight until Bisping's defense slipped. Henderson then landed another heavy right hand while Bisping was senseless and defenseless on his back before the referee tackled him.

"What happened?" Bisping asked Wolfslair Academy training mate Rampage Jackson as they walked to the locker room afterward.