Katie Taylor edged past Briton Chantelle Cameron via majority decision in a thrilling light-welterweight title fight in Dublin.
Ireland's Taylor avenged the only loss of her career in an extraordinary bout at 3Arena on Saturday to become a two-weight undisputed champion.
Taylor almost hit the deck in the final seconds, but stayed on her feet in a crucial moment for the scorecards.
One judge scored it a draw, while the other two were 98-92, 96-94 for Taylor.
"Whoever wrote me off obviously doesn't know me very well," she said. "Let's get the trilogy at Croke Park."
Fighting as the underdog for the first time in her career, Taylor joins Claressa Shields and Terence Crawford as the only two fighters to win undisputed championships in two different weights in the four-belt era.
Cameron fell to a first defeat of her 19-fight pro career, relinquishing her IBF, WBA, WBO and WBC light-welterweight titles in the process.
Taylor dubbed the bout her "real homecoming" and sent an already elated crowd into overdrive when she called for a deciding fight at the 80,000-seater Croke Park, the Gaelic games stadium which is also in the Irish capital.
The 37-year-old retreated in fight week after heartbreak six months ago but produced one of the best performances of her career to seal what will surely go down as her greatest victory.
Just like their first fight in May, the 3Arena was almost full more than two hours before the main event.
Wins for Irishmen Thomas Carty, Paddy Donovan and Gary Cully built towards the crescendo that was Taylor's ringwalk.
Earlier this year, Taylor's entrance lasted an age as she soaked in her first experience on home soil as a professional.
This time she walked first - a new experience in her 18th consecutive world title bout - and was already on her way to the ring before the traditional pre-fight taster 'Sweet Caroline' had stopped playing.
There was no lingering for Taylor this time around as she was straight down the ramp and through the ropes.
Standing in the corner Cameron did in their first encounter, Taylor waited for the champion who did a bit of shadow boxing on the ramp before entering the ring to a chorus of boos.
While Taylor showed little emotion, the partisan crowd showed their colours as they greeted the Bray native like a queen and relentlessly booed Cameron.
Taylor opened aggressively in the first round, pushing forward in a stark change of tactic from the first meeting. Cameron stood her ground as the Irish crowd roared behind every punch of Taylor's.
The home fighter suddenly hit the canvas, but it was ruled a slip. A frantic final 10 seconds saw Taylor land heavily on Cameron.
The Briton did not step back under the pressure as she looked to respond, but Taylor was able to duck away from danger - much to the delight of the arena.
Taylor's gameplan emerged in the chaos of the exchanges - she would wait for Cameron to come in and fire off counters in volume.
A cut appeared on Cameron's forehead in the third round from a clash of heads as the two women exchanged hooks on the ropes.
Taylor was in the ascendancy and her coach Ross Enamait urged her forward in the final seconds of the fourth round as the cut on Cameron's forehead widened.
The doctor was called to look at the gash but was quickly dismissed. Cameron might have been bleeding but refused to take a backwards step and began the fifth round strongly.
Taylor tried to push her back, but the champion kept pouring forward and clipped a moving Taylor with a lovely right hand.
The Northampton fighter tried to repeat her dominance in the sixth, but Taylor changed her approach and drew Cameron into short-range exchanges.
Cameron appeared to land heavily at stages and complained to the referee when Taylor would grapple as the half-way point arrived.
The two women came together again in the seventh round, each standing their ground as the incredible action refused to let up.
The crowd roared as Taylor returned to her corner at the end of seventh and booed when the referee warned the Irishwoman about holding moments later.
A rogue shoulder from Cameron struck Taylor in the eighth round and Cameron landed a beautiful uppercut seconds later.
The shot wobbled Taylor as she staggered backwards but the bell arrived just in time.
"Katie" rung out in the ninth round as Taylor was forced to walk through a Cameron storm of incredible pressure.
The Briton appeared to be somehow not feeling the pace, while Taylor started to wilt.
There was swelling on one of Taylor's cheeks as she was peppered with shots, but the challenger stayed on her feet.
The final round saw a moment of recognition between the two women as they touched gloves before the action resumed.
Taylor could not afford a knockdown and almost hit the deck in the final moments after some big shots from Cameron.
A 10-8 knockdown round for Cameron could have swung at least one of the scorecards, but Taylor was able to survive, sparking wild celebrations from her corner and in the stands.
There had been a nervous energy surrounding the fight all week and it reached its peak as the scores were read out.
The first scorecard was a 95-95 draw, heightening the tension further.
But the final two scorecards in Taylor's favour prompted elation in the crowd and the Irishwoman finally allowed herself to roar with them as her greatest victory was confirmed.
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