Jessica McCaskill handed Cecilia Braekhus her first professional defeat in a huge upset to become the undisputed world welterweight champion.
American McCaskill, 35, won by majority decision in Tulsa to take Braekhus’ WBA, WBC, IBF, IBO and WBO belts.
Victory would have seen Norway’s Braekhus, 38, beat Joe Louis’ streak of 25 straight title defences in an 11-year reign.
“This is for the fourth-grade-year-old homeless Jessica,” said McCaskill.
“This is for the little girl that just didn’t care what people thought about her and learned to love herself even though she was really weird.”
Braekhus, who became welterweight world champion in 2009, said: “If this is my last fight, I could leave women’s boxing and just say, ‘I was a part of this. I was a part of taking women’s boxing to this level.'”
