Ireland's Katie Taylor retained her undisputed lightweight world championship with a split decision win over Puerto Rican Amanda Serrano Saturday in a history-making, epic fight at Madison Square Garden.

The first women's bout to headline a fight card at the iconic New York venue in its 140-year history did not disappoint.

Brooklyn-based Serrano pummelled Taylor in the fifth round, but the bloodied champion held on and reasserted herself as the pair went toe-to-toe over the final rounds of a breathless contest to edge the decision and remain unbeaten after 21 professional bouts.

"I had to dig deep," Taylor said. "I knew I'd be in the trenches at some stage. She is a phenomenal fighter, a great, great person."

Serrano, the unified featherweight world champion, has 42 prior victories including 30 knockouts.

Despite stepping up two weight divisions to face Taylor, Serrano was more effective in the middle rounds and staggered the Irishwoman in the fifth.

Blood was flowing freely from Taylor's nose by the end of the sixth, but Serrano failed to press home the advantage and the Irishwoman regrouped to land the more telling shots in the seventh, eighth and ninth.

The 10th and final round saw them battling blow-for-blow until the final bell, when Canadian referee Michael Griffin gathered them in and the fighters exchanged a hug.

Judge Benoit Rousel scored it 96-94 for Serrano, but judge Guido Cavalleri saw it 96-93 for Taylor and Glenn Feldman scored it 97-93 for the champion.

"We put on a hell of a show," Serrano said in the ring. "Women can sell! Women can fight! We put on a show."

With a sellout crowd of 19,187 offering fierce support for both fighters, southpaw Serrano boxed on the front foot with a series of punishing blows snapping Taylor's head back in the fifth.

Serrano targeted Taylor's body in the sixth, but the champion fought back fiercely and the cheers were so loud at the end of the round that they drowned out the closing bell.

The 10th was a dogfight, the fighters trading punches in the center of the ring before Taylor emerged with her sixth defense of the undisputed title she has held since beating Delfine Persoon in 2019 to capture all four belts.

Her dominant professional career followed a stellar amateur career that included Olympic gold in London in 2012.

Serrano suffered only her second loss and her first for a decade having won 28 straight bouts since defeat to Frida Wallberg in April, 2012.

The prospects are that she could get another shot at Taylor with a lucrative rematch tempting both fighters.

"Let's do it again, Amanda," Taylor said, as they were interviewed in the ring.

"Whatever she wants," Serrano replied.