Greatest Heavyweight Upsets in Boxing History

A look back at some of the most shocking heavyweight results that changed careers and altered the sport’s landscape.

• Buster Douglas def. Mike Tyson (1990): In Tokyo, Douglas produced arguably the biggest upset in boxing history, stopping the unbeaten, undisputed Tyson in the 10th round and turning a supposed mismatch into a seismic shock.
• Leon Spinks def. Muhammad Ali (1978): A relatively inexperienced Spinks stunned the world by outpointing Ali to take the world heavyweight title, handing Ali one of the most unexpected losses of his career.
• Andy Ruiz Jr. def. Anthony Joshua (2019): A late replacement with long odds, Ruiz outworked and overwhelmed Joshua at Madison Square Garden to capture multiple world titles — a modern upset that reshaped the division.
• Hasim Rahman def. Lennox Lewis (2001): Rahman delivered a fifth-round knockout in South Africa to stun Lewis and claim the heavyweight crown in one of the era’s biggest surprises.
• Oliver McCall def. Lennox Lewis (1994): McCall’s second-round TKO over Lewis was a dramatic, unforeseen reversal that marked Lewis’s first professional loss.
• Corrie Sanders def. Wladimir Klitschko (2003): Sanders used devastating left-hand power to stop the then-rising Klitschko in two rounds, halting Wladimir’s momentum with a stunning knockout.
• Chris Byrd def. Wladimir Klitschko (2000): Byrd’s defensive and tactical mastery earned him a decision over the future long-reigning champion, a result few anticipated at the time.

Note about memories and myths: over decades, fans sometimes conflate bouts or misremember outcomes, but the documented upsets above are among the clearest examples of heavyweight shockers.

Common threads connect these fights: underestimation of the challenger, a single decisive shot or tactical gameplan, and nights when the favorite simply didn’t perform. Heavyweight boxing’s history is full of moments when one night changed everything — and that unpredictability is a key part of the division’s enduring appeal.