Carl Frampton became a two-weight world champion with a majority decision victory over Leo Santa Cruz in their WBA featherweight title bout in New York.
Former super-bantamweight champion Frampton, fighting for the first time at 122lbs, gave an assured, composed performance to stun his unbeaten Mexican opponent and score a 23rd professional success.
Judge Guido Cavalleri scored the contest 114-114 but Frank Lombardi (116-112) and Tom Schreck (117-111) ruled in favour of the Northern Irishman, giving him the belt his manager Barry McGuigan won in 1985.
Frampton was well drilled from the start, producing the sharper punches to lead on all three judges' cards by the end of the third round.
However, Santa Cruz - who won the title in August last year and was making his second defence on Saturday night at the Barclays Centre - settled down and had a productive sixth round.
Frampton, roared on by the majority of the supporters inside the Brooklyn venue, did absorb some punishment against a man well known for his intense work-rate.
Yet the Belfast fighter continued to look assured until the closing stages of the fight, when he was particularly tested by a right hand over the top from Santa Cruz in the penultimate round.
Both men seemed to tire in an even final round - but the verdict went to Frampton, giving him a title McGuigan won more than 31 years previously at Loftus Road when he defeated Eusebio Pedroza.
Frampton told BBC Radio 5 Live afterwards: "I'd like to thank my travelling support but also the Irish Americans. It was a tough fight...I wanted to be in a fight that people would remember.
"Leo Santa Cruz is a true warrior. I respect him a hell of a lot - and a hell of a lot more after that fight.
"I had a good gameplan - Shane McGuigan (Barry's son) is an unbelievable coach. I fought with my heart rather than my head sometimes but I'm glad I got my hand raised.
"The game was to hit him hard and make him earn my respect. I hurt him in the second round I think."
The 29-year-old now wants to defend the title in his home city and did not rule out a rematch, although he also has IBF champion Lee Selby in his sights.
Frampton added: "I'd love to bring him (Santa Cruz) to Belfast and show them an amazing fighter but I have a good relationship with Lee Selby's team. I want to be the best and be involved in big fights."
Santa Cruz immediately set his sights on a rematch, saying: "It was a pretty tough fight but now I want a rematch. I don't care where."
The 27-year-old added: "He's a great champion and he's got a very difficult style. It's hard to forget your first loss but I will go back to the gym and get a rematch."