Northern Ireland's Carl Frampton outpointed Spain's Kiko Martinez in Belfast's Titanic Quarter to secure the world IBF super-bantamweight title.
In front of 16,000 fiercely partisan fans in a purpose-built outdoor arena, Frampton controlled the fight throughout and floored the champion in the fifth round.
Martinez demonstrated remarkable durability to make it to the final bell but the judges scored the fight 119-108, 119-108, 118-111 - all in Frampton's favour.
The 27-year-old had knocked Martinez out last February to win the European crown, only for the Spaniard to win the IBF title six months later.
"I've got the world title!" Frampton told BBC Radio 5 live after adding the IBF belt. "I feel a bit emotional - it has been a long time coming, it has been a hard road.
"I intend to hang on to it for a very long time."
Frampton is managed and promoted by former featherweight world champion Barry McGuigan, who was such a unifying force during Northern Ireland's Troubles in the 1980s, and trained by Barry's son Shane.
McGuigan Sr said after the fight: "I love him like a son - he's a part of me and I know how talented he is.
"He showed us his bravery tonight and he certainly showed the skills he's got. He's really got a tremendous future ahead of him."
The victory for the Tiger's Bay native, which makes him his country's first world champion since fellow Belfast fighter Wayne McCullough in 1996, provided more cause for celebrations across Northern Ireland and beyond.
As well as the United Kingdom and Ireland, the fight was broadcast in the United States, South America, China, Japan and the Middle East.
As for McGuigan Sr, he will be relieved as well as elated, having pumped a huge amount of money into the event (it was the country's biggest gate for a boxing match by some distance) and brought Martinez over from Spain at considerable cost.
Martinez had defended his title twice since stopping Jhonatan Romero last August and promised to gain revenge over Frampton, the only man to knock him out in 35 previous fights as a professional.
|Born||21 February 1987, Belfast, Northern Ireland|
|Family||Lives with wife Christine and three-year-old daughter Carla in Lisburn|
|Boxing background||Started boxing at Midland ABC, Tiger's Bay before moving to Holy Family ABC in New Lodge as a professional|
|Connections||Managed by Barry McGuigan, trained by Barry's son Shane in London|
|Amateur record||125 fights, 114 wins, 11 defeats; two-weight Irish champion; European silver medal 2007; 12 international medals|
|Pro record||19 fights (13 KOs), 19 wins|
|Pro honours||World, European & Commonwealth super-bantamweight champion|
But overlooked by the famous Harland and Wolff cranes, next to where the Titanic was built and launched a little more than 100 years ago, Frampton was not to be denied.
He won a cagey first round courtesy of a couple of snappy right crosses before the fight opened up in the second, Martinez trying his luck with some swinging right hands and Frampton having success on the counter.
Frampton, fighting on the back foot for the most part, repeatedly made Martinez look clumsy in the third, suggesting that the champion was starting to unravel.
The challenger continued to control proceedings in the fourth, keeping the stalking Martinez at bay with jabs and two-shot combinations, although Frampton did mix things up with one juddering uppercut.
Martinez was lucky not to be docked a point at the start of the fifth, having hit a prone Frampton on the back of the head. But Frampton exacted sweet revenge, flooring his rival with a short, chopping right towards the end of the round.
Martinez, bleeding from the cut over his left eye, was up almost immediately and straight back at Frampton, but was picked apart some more in the sixth.
The seventh was Martinez's best round of the fight, the Spaniard landing with a couple of those looping right hands. But Frampton was back in control in the eighth, drawing Martinez on to some hurtful left-right combinations.
Frampton was showing a cut over the right eye at the start of the ninth, which was a difficult round to score, and the 10th round was grim stuff as both men traded toe-to-toe on the inside, although Frampton landed the cleaner shots.
A battered and bruised Martinez looked close to folding in the 11th as Frampton rained blows upon him, but the man from Alicante proved that he is as game as they come by extending the contest into the final round.
Martinez looked ready to go again midway through the 12th but was still trading blows when the final bell sounded. But the result was never in doubt.
Frampton is now one of five world champions from the United Kingdom, alongside Carl Froch, Kell Brook, Scott Quigg and Jamie McDonnell, although those last two hold lesser versions of titles.
British fight fans would now like to see Frampton fight Bury's WBA title-holder Quigg but American Chris Avalos is the IBF's mandatory challenger.
Martinez was given special dispensation to fight Frampton instead of Avalos but the 24-year-old Californian is likely to get his chance next spring, especially given that he recently teamed up with British promoter Eddie Hearn.
Quigg, 25, defends his portion of the WBA title (Cuba's Guillermo Rigondeaux is their so-called 'super' champion and regarded as the best in the division) against Belgium's Stephane Jamoye in Manchester on 13 September.
But Frampton, who emerged from his triumphant night with a badly marked face and a damaged hand, will now take a well-earned holiday with his wife Christine and daughter Carla before weighing up his options.
BBC Radio 5 live Sports Extra will be replaying commentary of the fight in full at 0900 on Sunday morning.