Claressa Shields defended her undisputed heavyweight crown by beating fellow American Franchon Crews-Dezurn by unanimous points decision at Little Caesars Arena in Detroit.
In her first outing of an $8m (£6.1m) multi-fight deal, Shields was a 100-90 victor on the scorecards of all three judges as she retained her WBO, WBA, IBF and WBC titles.
The 30-year-old is unbeaten in 18 professional outings following the 10-round bout, which included plenty of fiery exchanges between Shields and 38-yer-old Crews-Dezurn.
"I felt like I had to take my time. Franchon hits hard and she's tough," said Shields.
"She was trying to cause an upset and got me with some shots.
"She's a heavy-hitting diva and that's one of the best fights I've been in my professional career, especially at 10 rounds. It was fun. I had to watch my ass every round.
"I think today I showcased my skills, my offence, my defence and body shots. I almost had her out in round seven, but she just wouldn't go."
Shields beat Crews-Dezurn three times as an amateur and on their professional debuts in 2016.