Conor McGregor knocks out Jose Aldo in 13 seconds

Conor McGregor, left, fights Jose Aldo during a featherweight championship mixed martial arts bout at UFC 194, Saturday, Dec. 12, 2015, in Las Vegas. (AP Photo/John Locher)

LAS VEGAS -- (The Notorious) Conor McGregor backed up his trash talk with his fists Saturday night at UFC 194, knocking out Jose Aldo in just 13 seconds to become undisputed featherweight champion.

It was short and violent -- the fastest finish in UFC championship history. And it ended the mystique of Aldo as the best pound-for-pound MMA fighter on the planet while making the brash Irish 145-pounder the UFC's main man.

Aldo missed with a right and McGregor floored the champion with a left, adding a pair of hammer-fists before referee John McCarthy stepped in before a stunned crowd of 16,516 at the MGM Grand Garden Arena.

"I knew he would overextend and I knew I would catch him," said McGregor, who held his own post-fight news conference after the other fighters left the dais.

"I respect Jose. I wish him well. But now we are onto the next chapter," added the new champion, who had predicted a first-round finish.

Aldo (25-2-0) had won his last 18 fights and not lost since November 2005. McGregor (19-2-0) has now won 15 straight dating back to November 2010.

The previous fastest finishes in a UFC world title fight were Ronda Rousey's 14-second submission of Cat Zingano in February and Andrei Arlovski's 15-second KO of Paul Buentello in 2005.

Aldo entered the cage as champion while McGregor arrived as interim title-holder for a win over Chad (Money) Mendes while Aldo was out injured.

McGregor, who won a US$50,000 bonus for performance of the night and likely millions more from what is expected to be one of the UFC's biggest-ever pay-per-view takes, left with the one and only belt after a title fight whose action could be captured in a Vine with seconds to spare.

"I think we need a rematch. It wasn't really a fight," Aldo said through an interpreter.

The UFC laid out two possible scenarios for McGregor. He could stay at featherweight and make his first title defence against Frankie (The Answer) Edgar. Or he could vacate the 145-pound championship and move up to lightweight to fight for the 155-pound title.

"The options are there now ... I enjoy options. Options are a good thing in the fight game," said McGregor, who held both titles in England's Cage Warriors promotion.

But he rejected the idea of giving up one belt to fight for another.

The crowd roared as McGregor -- clad in green compression shorts -- entered first, with "Ole Ole" chants from the stands competing with his Notorious B.I.G. entrance music. Aldo followed him to "Run This Town" by Jay-Z with Rihanna and Kanye West.

The two did not touch gloves before the opening round. The end came soon after.

"I had a little moment when I felt sorry for Jose," said McGregor.

FightMetric said McGregor landed five significant strikes to one for Aldo, whose lone hit was a left that connected as he toppled face-first to the canvas.

In the co-main event, No. 1 contender Luke Rockhold dethroned middleweight champion Chris Weidman.

Rockhold (15-2-0) beat Weidman up on the ground in the third round and did the same in the fourth, before referee Herb Dean finally stepped in at 3:12.

"It was Luke's night," said Weidman, his face a road map of cuts and welts.

Two judges had Rockhold ahead 30-26 going into the fourth round while the third judge had it 29-27 for the challenger.

The fight turned in the third when Weidman tried a spinning wheel kick. Rockhold evaded the kick, grabbed Weidman and took him down for the first time in his UFC career. Rockhold then mounted Weidman and carved his face open with repeated strikes. The beatdown seemed to go on forever, with Dean allowing the round to end.

Weidman's face was a mess as he came out for the fourth. He soon found himself on the bottom again and the beating continued.

"I could not believe he came out in the fourth round," said Rockhold, who also noted he had been on antibiotics for a staph infection the last two weeks.

Weidman (13-1-0) had previously beaten a Who's Who of opponents, including former champions Anderson Silva (twice), Lyota (The Dragon) Machida and Vitor (The Phenom) Belfort.

Kicking Weidman took a toll. Rockhold, a former Strikeforce champion, limped out of the cage with the title.

Rockhold and Weidman, who was taken to hospital to be checked out, each collected a $50,000 bonus for fight of the night.

The 29-year-old Aldo, who at five foot seven is two inches shorter than the Irishman, was ranked the UFC's top pound-for-pound fighter. McGregor, 27, was No. 12 in the pound-for-pound rankings, just below Rousey.

Asked if he was now No. 1, McGregor said: "I believe so."

Aldo and McGregor were originally slated to meet at UFC 189 in July. And the fighters talked smack in Toronto, Rio de Janeiro, Las Vegas, Los Angeles, Boston, New York City and Dublin, criss-crossing North America in separate private jets before heading to Europe to hype that fight.

They almost came to blows in Toronto when McGregor slapped Aldo on the back while waiting to go on air during a morning visit to CTV's "Canada AM."

White dubbed it the "war tour."

But Aldo withdrew less than two weeks before the fight due to a rib injury. McGregor fought Mendes instead, stopping him late in the second round for the interim title.

The sandpaper-like McGregor, a former plumber who has yet to meet a microphone or camera he doesn't like, had taken one verbal shot after another at Aldo, whose lack of English restricted his comebacks. But the Brazilian looked calm and businesslike in the buildup to this fight.

Aldo was the only undisputed featherweight champion the UFC has ever had. He won the 145-pound crown in the WEC in November 2009 and became UFC champ a year later when the UFC bought and absorbed the WEC.

The win earned McGregor a spot on the cover of the UFC's next video game, alongside Rousey.

Yoel (Soldier of God) Romero, ranked third among middleweight contenders, hung on to win a split (29-27, 28-29, 29-28) decision over No. 2 Ronaldo (Jacare) Souza of Brazil.

Romero won his seventh straight while snapping Souza's eight-fight win streak.

"I am ready for everybody," said Romero.

Romero took it to Souza on the ground in the first round after dropping him with a spinning back fist. The wobbly Brazilian was unsure where to go when the round ended. Souza recovered and hurt Romero, who ran out of gas as the fight progressed, at the fence in the third before taking him down.

Romero, 38, won a silver medal in freestyle wrestling for Cuba at the 2000 Olympics. Souza, 36, is a former Strikeforce title-holder and world Brazilian jiu-jitsu champion.

Demian Maia, another former jiu-jitsu world champion ranked sixth among welterweight contenders, outgrappled No. 12 Gunnar (Gunni) Nelson -- a black belt himself -- while administering plenty of ground-and-pound pain along the way to a lopsided 30-26, 30-25, 30-25 decision.

Max (Blessed) Holloway, ranked fifth among featherweight contenders, beat No. 8 Jeremy (Lil' Heathen) Stephens by a unanimous (30-27, 30-27, 29-28) decision for his eighth straight win.

Montreal lightweight John (The Bull) Makdessi, returning after a broken jaw in a loss to Donald (Cowboy) Cerrone, lost a split decision to Yancy Medeiros on the undercard.