Katie Taylor beat Amanda Serrano by unanimous decision to defend the undisputed super-lightweight championship and complete a clean sweep of three victories in their trilogy.
After their 10-round clash for the WBO, WBC, IBF and WBA 140lb titles at Madison Square Garden, Taylor was declared winner by scores of 97-93 on two of the judges' cards, while the third had them even at 95-95.
It was the third-straight close contest between the two, after Taylor won a split decision in their first bout and a narrow unanimous victory in the second.
Back in Madison Square Garden, the site of their first fight, Taylor improved her record to 25-1 (6) in a bout that might not have been as exciting as their first two, but was similarly almost too close to call.
Serrano, 47-4-1 (31), never really hurt Taylor on this occasion, expected to be the pair's final fight.
It was a festive atmosphere in front of another sold-out crowd of more than 19,000 split between Irish and Puerto Rican fans with the historic arena hosting its first all-women's card. Serrano was all smiles on a joyous ring walk accompanied by the Knicks City Dancers.
There were barely any meaningful punches in the first round. By the third they were trading shots and both were landing flurries. But Serrano seemed to fight more cautiously than she had before against Taylor, keeping her distance, perhaps wary of clashing heads which had left her cut in their second fight.
Taylor looked to control the centre of the ring and landed some good counter shots as she drew Serrano onto her.
Several rounds could have gone either way as the fight built to a tense climax, Serrano coming forward more and forcing Taylor into a corner in the fifth round, but the champion fought her way out.
Taylor was marked under the right eye in the eighth, but edged the final two rounds to secure the verdict.
Ruling out a fourth meeting with the Puerto Rican, Taylor was cagey about whether she would continue to fight.
"I don't know, I just don't want to fight Amanda Serrano again. She punches too hard," she said after the bout.
"I have a huge ton of respect for Amanda, she's such a warrior. It's a pleasure to share a ring with her.
"We have made history three times. We are history makers forever.
"I thought I was boxing very smart, she wasn't able to catch me very much tonight. But it's always close against Amanda."
Serrano reflected she'd tried to work "smarter not harder" this time against Taylor.
"We tried to stay with the long punches and one twos," she said, "and it just wasn't enough."
Savannah Marshall suffered a shock defeat on her return to boxing. After a sojourn in MMA, Marshall, formerly an undisputed super-middleweight champion, lost to Shadasia Green in an IBF and WBO title unification at 168lbs.
The decision was split. One judge awarded the fight 96-93 to Marshall but America's Green was awarded the verdict 95-94 and 96-93 by the other judges despite a point deduction for holding.
Ellie Scotney ended Mexican Yamileth Mercado's six-year reign as WBC super-bantamweight world champion with a comprehensive unanimous verdict.
The 27-year-old from Catford added the WBC title to her IBF and WBO crowns with a 100-90, 98-82 and 98-82 decision win.
England's Chantelle Cameron, a former two-weight world champion, had a comfortable unanimous points decision over Jessica Camara, while Ramla Ali returned to the ring after a year out with a tighter unanimous verdict over Lila Furtado.
American Alycia Baumgardner retained her undisputed super-featherweight title with a unanimous decision over Spain's Jennifer Miranda.
