Richard Johnson, 24, was convicted of killing Joshua Bradley, 19, in the fight on 8 February by a jury at Nottingham Crown Court.
The court heard Mr Bradley had been trying to help a friend who was being assaulted when he was fatally injured.
Johnson, of Hyson Green, was told he must serve at least 25 years before he is eligible for release.
Mr Bradley was pronounced dead at the scene in Thurland Street, Nottingham.
A second defendant, Zaiem Zulqurnain, 19, of Newlyn Drive, Aspley, was found not guilty of murder and also cleared of violent disorder.
The jury was earlier instructed to find Muhamed Adnan, 22, of Middleton Boulevard, not guilty of murder.
He had already admitted violent disorder and will be sentenced later.
Mr Bradley had been a boxer since he was seven years old. He was a Nottinghamshire and Lincolnshire youth champion and represented England at youth level, according to the Nottingham Post.
After his mother's death in his early teens he gave up the sport but continued to help young members at Bilborough Boxing Club, the newspaper reported.
Det Supt Kate Meynell, of Nottinghamshire Police, said: "This was a wholly unnecessary death of a young man in the prime of his life.
"Johnson purposefully took out a knife into the city centre, and brandished it when the fight broke out in a state of bravado.
"Joshua, who was an accomplished boxer, went to help a friend who was being assaulted but tragically ended up losing his life.
"For Joshua's family and friends, that night changed everything.
"They will never see Joshua again, they didn't get a chance to say goodbye and now have to try to go on without him."
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