LAS VEGAS — For the second consecutive year, Hawai'i sports fans will return home from the Mainland with the worst kind of omiyage — the bitter taste of a loss.

Last year, it was the Hawai'i football team at the Sugar Bowl. Last night, it was Hilo's BJ Penn in the main event of the UFC 94 mixed martial arts card.

Both were blowouts.

Canada's Georges St-Pierre stunned Penn — and the thousands of Hawai'i fans who followed him to Las Vegas — with a dominating victory in what was one of the most anticipated and hyped bouts in the history of the prestigious UFC organization.

"Georges said he was going to come out and he was going to dominate BJ Penn and prove he was the best fighter, and I think he did that," UFC president Dana White said.

An announced crowd of 14,885 at the MGM Grand Garden Arena watched St-Pierre beat Penn for the second time in his career. The first one came in March 2006 via a razor-thin split decision.

This one was far more decisive.

The bout was called after four rounds at the advice of a ringside doctor who inspected Penn in between the fourth and fifth rounds.

Penn was taken to a hospital immediately after the bout and did not attend the post-fight press conference.

The bout was scheduled for five 5-minute rounds.

St-Pierre improved to 18-2 and successfully defended his UFC welterweight (170 pounds) world championship. It will go in the record books as a TKO.

"This is the best day of my career so far," St-Pierre said.

Penn, who is still the UFC lightweight (155 pounds) world champion, dropped to 13-5-1. He was seeking to become the first fighter in UFC history to own championships in two separate weight classes at the same time.

Instead, St-Pierre dominated Penn like no other MMA competitor has before. St-Pierre was listed as the favorite in Las Vegas casinos, but the one-sided nature of the bout was still a surprise.

St-Pierre used his strength and weight advantage to stay on top of Penn and land numerous strikes throughout the duration of the bout.

Both fighters made the 170-pound weight limit on Friday, but St-Pierre said he weighed "approximately 185, 187" pounds when last night's fight started. Penn came in at 168 during the official weigh-in, and probably did not weigh more than 170 last night.

"That's why my strategy was to make a clinch in the first round," St-Pierre said. "Make him push me away and make him carry my weight and make his shoulders tired."

The first round was mostly about defense. St-Pierre attempted several single-leg takedowns, but Penn stayed on his feet.

"After I saw that first round and Georges had a hard time taking him down, I thought it might be like that for a couple of rounds," White said.

Instead, the momentum took a significant turn in the second round.

St-Pierre got Penn to the ground one minute into the second round, then stayed in the top position for the next four minutes. St-Pierre landed numerous devastating punches to Penn's face during those four minutes. When the round ended, Penn staggered to his corner.

"My game plan was to make the first round and second round a clinch, mostly like a wrestling match," St-Pierre said. "BJ Penn has very good hand speed, so I wanted to make him tired by carrying my weight and all the blood comes out from his shoulder. Then his hands would not be as fast later in the fight."

By the third round, blood was pouring out of Penn's nose. St-Pierre was then able to take Penn down again and continue the ground-and-pound assault.

Early in the fourth round, St-Pierre pinned Penn's arms to the mat and proceeded to land several unanswered elbows and punches to Penn's face.

By then the outcome was inevitable.

To his credit, the gritty Penn never surrendered, and even tried to maneuver his way out of St-Pierre's grasp late in the fourth round.

"At the end of the fourth round, I was trying to finish him hard," St-Pierre said. "But he always survived. He's a very tough guy."

Penn's face was bloodied and bruised, and he appeared on the verge of collapse when the ringside doctor called it off.

White said he would advise Penn to stay in the lightweight division from now on.

"I don't think I'll have to encourage him to do that," White said.

White added that Penn's next bout will likely be a lightweight title defense against Boston's Kenny Florian.

St-Pierre will probably defend his welterweight title next against Brazil's Thiago Alves.

Despite last night's impressive performance, White said he would not put St-Pierre at the top of the UFC's overall pecking order just yet.

"I still wouldn't call him the best pound-for-pound in the world," White said. "But I'd say he's No. 2."

Brazil's Anderson Silva, the UFC middleweight (185 pounds) champ, is considered the No. 1 pound-for-pound fighter. If St-Pierre defeats Alves, it could set up the next super fight with Silva.

Before St-Pierre took control of last night's bout, the deafening chants alternated between Penn's Hawai'i fans and St-Pierre's Canadian fans.

St-Pierre was classy in victory, acknowledging all the fans.

"I know the economy is not very good right now," he said. "So I have to say thanks to all the fans for their support. Canadian and also Hawaiian, and also American, and from around the world who came to support us tonight."

St-Pierre did acknowledge that some of Penn's trash talk during the UFC Primetime preview series gave him added motivation.

"I was not fighting for this, the belt," he said. "I was fighting for the name, BJ Penn. And of course, he put in some extra motivation when he said some things about me and the people I like."

In the semi-main event, Lyoto Machida remained undefeated in the 205-pound division with a knockout victory over fellow Brazilian Thiago Silva.

Machida landed a devastating right hand to the head of Silva, who was lying on his back when he received the punch. It came just before the horn sounded to end the five-minute first round.

Both fighters entered the bout undefeated. Machida is now 14-0 and considered one of the top contenders to face light heavyweight champion Rashad Evans.

Silva dropped to 13-1.

IN OTHER BOUTS

205: Jon Jones def. Stephan Bonnar by unanimous decision.

170: Karo Parisyan def. Dong Hyun Kim by split decision.

155: Clay Guida def. Nate Diaz by split decision.

170: Jon Fitch def. Akihiro Gono by unanimous decision.

155: Thiago Tavares def. Manvel Gamburyan by unanimous decision.

170: John Howard def. Chris Wilson by split decision.

205: Jake O'Brien def. Christian Wellisch by split decision.

170: Dan Cramer def. Matt Arroyo by split decision.