Lee McGregor set aside fellow Scot Kash Farooq over the controversial split decision to add the British bantamweight title to the Commonwealth belt after an exciting battle.
With two judges scoring 114-113 for each boxer, the third proved decisive – with McGregor taking it 115-112 at the Glasgow Emirates Emirates Arena.
This is Farooq's first defeat in 14 battles, while McGregor is now 8-0.
"My strong final result made me win the fight. My heart and desire," said McGregor, 22.
Farooq, 23, appears to have done quite a lot in his hometown after landing a cleaning blow, with the verdict greeted with shock by many in his capacity.
But after reaching one point to defend in the 10th round, Edinburgh fighter McGregor finished strongly to tie the belt together. And he dedicated a thrilling victory to family members who had just died.
"I want to pay special attention to my aunt, my father's sister, whose birthday is tonight," said the 22-year-old man. "We just learned the bad news this weekend that he has died.
"I had a terrible week, making weight, dealing with it. I feel like I have an army with me tonight and that's what pulls me."
Considered the biggest all-Scottish battle in more than a decade, the battle did not disappoint. McGregor tried to force himself early on but was rocked by three big hits from Farooq in the second half.
McGregor responded well, opening the wound under his opponent's right eye, before landing a succession of cut values in the seventh. However, Farooq's harsh attitude seemed to help him regain momentum and his "jump jump" proved an effective weapon.
After being reduced, McGregor, perhaps feeling he needed a knockout, went bankrupt and the pair pounded until the last bell.
"I will be sure I have won the fight, but with the points I know it will be very close," added McGregor. "A fair game for Kash, he is a small man who is gritty and keeps coming and pushing. But I feel that those things are careless when I get a bigger blow."
'Judge is mistaken' – reaction
Former world super featherweight champion and WBO Commonwealth, Alex Arthur
For me it was the wrong decision – I had Farooq won with a few rounds. I think his better variety of work and cleaner punches and the dominance of his ring – he always pushes forward to make things happen – makes him fight.
Most people also think that Kash has won. But it was an unbelievable battle and these two men could continue to be world champions.