Jamel Herring upset Masayuki Ito by unanimous decision to win the WBO super-featherweight title in Florida on Saturday.
Herring (20-2) took control after an even start in Kissimmee to claim a surprise victory.
Judges scored the fight 118-110, 118-110 and 116-112 in the American's favour, ending Ito's 10-month reign as champion.
Herring put Ito down with a right hook in the 11th round, but it was ruled a slip after the 28-year-old's glove touched the canvas.
The American had already dominated most of the fight, however, before judges awarded him his victory.
For Ito (25-2-1), it was his first defeat since 2015.