Amir Khan outclassed and outpointed Andreas Kotelnik to claim the WBA light-welterweight crown in emphatic fashion at the MEN Arena in Manchester.
Khan, 22, controlled the contest throughout, using his greater hand-speed and jab to frustrate and confound his Ukrainian opponent.
Khan landed 170 punches to Kotelnik's 80 and was awarded the fight 120-108 and 118-111 (twice) by the judges.
It was only Khan's 22nd bout since turning professional in 2005.
Bolton fighter Khan said beforehand that his shock knockout defeat to Breidis Prescott last September had transformed him from a boy into a man, and that seemed to be the case.
And the fingerprints of venerable American trainer Freddie Roach, who hooked up with Khan after that Prescott loss, were all over his victory over the gnarled Kotelnik, a veteran of 34 pro fights.
I took a few shots but I didn't rush. I used to but those amateurish mistakes have gone
Kotelnik, who was narrowly defeated by Bradford's Junior Witter in 2005 and who claimed the WBA title from Welshman Gavin Rees last March, was expected to pose a formidable threat.
But the Ukrainian never really got a handle on the contest as Khan showed vastly improved defensive skills and dictated proceedings from start to finish.
"It's the best feeling ever, I want to thank Freddie Roach and my team for making this happen. I'm a world champion and I'm going to enjoy it," Khan told BBC Sport. "I'm still young and I've got big things to come.
"I listened to him [Roach] and just listening to [Roach's Filipino multi-world champion] Manny Pacquiao, he took me to a different level. I took a few shots but I didn't rush. I used to but those amateurish mistakes have gone."
Khan took the opening session, bouncing in and out of range and peppering Kotelnik with jabs, although he did leave himself open once or twice when leading with his right hand.
It was more of the same in the second, with Khan once again outworking the champion, although Kotelnik, like Khan an Olympic silver medallist at lightweight, did manage to land with a sturdy right hand.
Kotelnik tested Khan's chin with another right hand early in the third, but the challenger hit back with a flurry of punches and controlled the rest of the round with his jab from range.
Despite Khan's superior speed and movement, Kotelnik blocked most of what Khan had to offer in round four, and there were signs the seasoned Ukrainian was warming to the task.
Kotelnik landed with a cuffing right hand midway through the fifth, but Khan stood up to it and looked to have nicked the round with more in and out raids.
Kotelnik started to show signs of frustration in round six, missing with some wild round-arm shots, and Khan got through with a razor sharp left hook as he continued to dictate on the back foot.
Khan landed with some sweet counters in the early stages of round seven before snapping Kotelnik's head back with a nice left-right combination as the Ukrainian showed the first signs of fatigue.
Kotelnik landed with a left-hand combination to body and head midway through round eight, but Khan was maintaining his high work-rate and had the crowd buzzing with some neat escapology on the bell.
Khan took a breather in the next and was caught with a right and a left on the bell as Kotelnik, sensing he was in need of a knockout, began to dig in and wind up with his shots.
But the raggedness did not last, with Khan recharged in round 10 and strafing his rival with slick combinations which, although not always landing, were enough to keep Kotelnik at bay.
Khan soaked up another Kotelnik right early in the next session, although there were a few danger signs as the challenger began to tire and the champion searched in vain for a knockout punch.
But Kotelnik was unable to pin his man down in the final three minutes, and Khan held firm to become the third-youngest British world champion since the Second World War, after Naseem Hamed and Herbie Hide.
Earlier, all three of promoter Frank Warren's former amateur stars made it three wins from three professional contests.
Olympic middleweight champion James DeGale enjoyed a rapturous reception before defeating Northern Ireland's Ciaran Healy in the first round.
Super-middleweight DeGale was calculated but aggressive as he peppered Healy's head and body, with a left-right to the ribcage flooring the Belfast man.
He stepped up the assault with the round coming to an end and just as the bell went, Healy's corner threw the towel in.
Amateur world lightweight champion Frankie Gavin enjoyed a second-round stoppage win over York's Graham Fearn, flooring his opponent twice.
And DeGale's fellow Olympian Billy Joe Saunders had little trouble seeing off Matt Scriven, who entered the ring having lost his last 27 consecutive fights, in the second round.
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