That record remained unmatched for 60 years until Floyd Mayweather Jr. equaled it by defeating Andre Berto in September 2015. Two years later, Mayweather returned from retirement to face UFC star Conor McGregor, who had never competed in a professional boxing match. The mismatch allowed Mayweather to score a 10th-round stoppage and retire at 50-0, moving past Marciano and becoming the owner of boxing’s most celebrated unbeaten record.
Not every great champion made it that far.
Joe Calzaghe retired undefeated at 46-0 after victories over Bernard Hopkins and Roy Jones Jr. in 2008. Calzaghe overcame a first-round knockdown to edge Hopkins by split decision before closing his career with a comfortable win over Jones at Madison Square Garden.
Larry Holmes came within one victory of matching Marciano before losing his 49th fight to Michael Spinks in 1985. Holmes famously vented his frustration afterward, declaring that “Marciano couldn’t carry my jockstrap,” a quote that has remained part of boxing lore ever since.
Several other champions also saw perfect records disappear in their late 40s. Poland’s Dariusz Michalczewski lost for the first time after beginning his career 48-0, while Paul Spadafora reached 48-0-1 before suffering his first defeat. Ricardo “Finito” Lopez retired officially unbeaten at 51-0-1, with the lone draw preventing him from finishing with a perfect record.
Today, the focus is no longer on matching Marciano’s 49-0. The benchmark is Mayweather’s 50-0, a record that appears even more difficult to reach in an era when elite fighters compete less frequently but against deeper competition.
The active fighter closest among boxing’s elite is unified junior middleweight champion Jaron “Boots” Ennis, who improved to 36-0 by stopping Xander Zayas on June 27. Ennis still has a considerable distance to travel, but at 29 years old he has time to continue building his record if he remains active and continues winning.
History suggests, however, that reaching 50-0 is far more difficult than it appears. Injuries, mandatory challengers, elite opposition and Father Time have ended the unbeaten runs of many great champions. Marciano held the standard for six decades before Mayweather surpassed it, and the list of fighters who came close is much longer than the list of those who actually finished the job.
