JUNIOR DOS SANTOS flattened Frank Mir with a huge right hand and finished him on the ground at 3:04 of the second round last night, emphatically defending his heavyweight title at UFC 146.

Dos Santos (15-1) picked apart the two-time ex-champion with superior boxing throughout the fight, eventually stunning Mir before finishing him with one last blow to the head. Dos Santos then wrapped himself in the Brazilian flag while celebrating his first title defense since taking the belt from Cain Velasquez last fall.

“I’m feeling awesome!” the ever-smiling Dos Santos shouted to the pro-Brazilian crowd. “It’s not bad for a nice guy, huh? … Frank Mir is a really good fighter, too. I came here to defend my belt, and I did it.”

Velasquez stopped Antonio “Bigfoot” Silva late in the first round after administering a bloody beating that both thrilled and horrified fans at the MGM Grand Garden. Roy Nelson, Stipe Miocic and Stefan Struve also won on a pay-per-view card topped with five heavyweight fights, a first in UFC history.

Dos Santos never faced trouble in the fight’s eight minutes after easily avoiding an opening-minute takedown attempt by Mir, who hoped his superior jiu-jitsu skills would allow him to avoid Dos Santos’ unparalleled striking ability. Mir, who turned 33 on Thursday, has the most heavyweight victories in UFC history, but he couldn’t match Dos Santos’ skills.

“He’s a champ,” Mir said. “He’s fast. I couldn’t get out of the way. He hit me hard. There were just too many of them, and they were hard shots. I couldn’t do anything about it.”

Dos Santos kept the fighters on their feet — except when he staggered Mir late in the first round and again midway through the second. Mir stumbled back several steps after Dos Santos’ decisive right hand, and Dos Santos added one last head shot before referee Herb Dean saved Mir.

“That surprised me a lot,” Dos Santos said. “Man, this guy can take a punch. My hand is hurt.”

Dos Santos downplayed the revenge element of beating Mir, who broke the arm of Dos Santos’ mentor, Antonio Rodrigo Nogueira, in a fight last December. Mir (16-6) had won three straight fights since losing a title shot to Shane Carwin in March 2010, but couldn’t reclaim the belt he held in 2004 before getting into a serious motorcycle accident and again in early 2009 before losing to Brock Lesnar.

Velasquez (10-1) finished Silva at 3:36 of the first round, but only after pulverizing the 6-foot-4 Brazilian with a relentless series of blows after an early takedown. Silva (16-4) was cut on his face early in the beating, sending streams of blood down his face and onto the canvas, eventually coating both fighters’ torsos.

“I knew he was going to be a tough guy to finish, and he posed certain threats,” Velasquez said. “But I’m happy I was able to go in there and perform. I took my time and waited to get good position to turn it on and finish the fight.”

The fight was stopped once to allow Silva’s corner to clear the blood from his eyes, but Velasquez promptly resumed the beating until the fight was finished. The former Arizona State wrestler was ferociously impressive in his first bout since losing the belt to Dos Santos in just 64 seconds during the UFC’s first prime-time Fox show.

“What you’ve done in the past, you’ve got to get over that,” Velasquez said. “This is a step in the right direction.”

The 32-year-old Silva appeared to be outmatched in his UFC debut after a lengthy MMA career highlighted by his dominant Strikeforce victory over Fedor Emelianenko in February 2011.

Earlier, Nelson stopped Dave Herman with an overhand right just 51 seconds into the first round, and Miocic remained unbeaten with a second-round stoppage of fellow heralded prospect Shane Del Rosario. Struve, the 6-foot-11 Dutch heavyweight, stopped Lavar Johnson in the first pay-per-view fight.

He led Quins to a first title yesterday and now Conor O’Shea wants more

In form: Morrison signals Olympic intent in Madrid