Lee McGregor edged out fellow Scot Kash Farooq on a controversial split decision to add the British bantamweight title to his Commonwealth belt after an engrossing battle.
With two judges scoring the fight 114-113 in favour of each boxer, the third proved decisive - with McGregor taking it 115-112 at Glasgow's Emirates Arena.
It is Farooq's first defeat in 14 fights, while McGregor is now 8-0.
"My strong finish won me that fight. My heart and desire," said McGregor, 22.
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Farooq, 23, looked to have done enough in his home city after landing the cleaner hits, with the verdict greeted with shock by many in the capacity crowd.
But after being docked a point for holding in the 10th round, Edinburgh fighter McGregor finished powerfully to unify the belts. And he dedicated the thrilling victory to a family member who recently died.
"I want to give a special mention to my auntie, my dad's sister, whose birthday it was tonight," the 22-year-old said. "We just found out the terrible news this weekend that she has passed away.
"I've had a horrendous week, making weight, dealing with that. I feel like I had an army with me tonight and that's what pulled me through."
Billed as the biggest all-Scottish bout in over a decade, the fight did not disappoint. McGregor tried to impose himself early on but was rocked on his heels by three big hits from Farooq in the second round.
McGregor responded well, opening a cut below his opponent's right eye, before landing a succession of juddering uppercuts in the seventh. Farooq's superior workrate, though, seemed to help him regain the momentum and his "jumping jab" proved an effective weapon.
After the deduction, McGregor, perhaps feeling he needing a knockout, went for broke and the pair traded thumping blows until the final bell.
"I would have been confident I had won the fight, but with the point off I knew it would be very close," McGregor added. "Fair play to Kash, he's a gritty little guy and kept coming and kept pushing. But I felt it was tippy-tappy stuff whereas I was landing the bigger shots."
'Judges got it wrong' - reaction
Former WBO world super-featherweight and Commonwealth champion Alex Arthur
For me it was the wrong decision - I had Farooq winning by a couple of rounds. I thought his better work variety and cleaner punches and his ring dominance - he was always pushing forward looking to make something happen - edged him the fight.
Most people ringside as well seemed to think Kash had won. But it was an unbelievable fight and both these men can go on to become world champions.