Some fans believe that Katie Taylor was knocked down early in her epic showdown with Chantelle Cameron, before coming back to claim a majority decision victory.
The Bray Bomber defied the odds to win 95-95, 98-92, 96-94 to become a three-division world champion and a two-division undisputed champion.
But there was cause for concern among the 13,000-strong crowd in Dublin when Taylor hit the canvas in the opening round. The referee ruled that she had simply slipped, and ruled out a knockdown.
However, it has not stopped online debates discussing whether it should have been classed as a knockdown.
ProBox TV showed a clip of the incident on X (formerly Twitter), accompanying the caption: 'WAS THIS A KNOCKDOWN?'
Some fans believe Katie Taylor was knocked down early in her fight with Chantelle Cameron
It has split viewers online, with some calling it a knockdown, and others citing a simple slip
One user replied: 'Definitely a knockdown. It looks like she may have stepped on her foot at first glance but she caught her clean and dropped her.'
'100% and would have changed the scorecards massively', concurred another fan.
However, not everyone agreed that it was a knockdown. 'Looks as Taylor either tripped or got her foot stepped on,' one X user stated, noting: 'Cameron did not complain at all.'
Another wrote: 'Even with the knockdown, Taylor still edged it. Tremendous respect to both women!'
Some X users argued that it was definitely a knockdown, and would have changed the fight
Others felt that it was a slip or trip, and noted that Cameron did not complain about the call
The effort of Taylor saw her called an 'Irish sporting legend' for edging the contest, which was also hailed as 'fight of the year' for the way Cameron challenged the Bray Bomber all the way.
Taylor is just the second boxer in history - male or female - to hold all four of boxing's major titles simultaneously in two weight classes in the four-belt era.
She was visibly shocked at her achievement after the decision was announced, but was looking ahead to a potential trilogy bout in front of another Irish crowd.
'Oh my gosh. Two-weight undisputed champion, that sounds very nice!' she said. 'That was the longest six months of my life waiting. This is my real homecoming.
'Whoever wrote me off doesn't know very well. Don't ever doubt me. The last fight you saw the worst of me and the best of Chantelle and it was still a close fight. Tonight you saw the real me and nobody can beat me.
'Let's get the trilogy at Croke Park!'
Taylor was overcome with emotion at the end of the fight, before calling for a trilogy fight