The only heavyweight boxing champion to retire with an undefeated professional record is Rocky Marciano.

Quick Scoop

  • Rocky Marciano retired as world heavyweight champion with a perfect record of 49 wins, 0 losses, and 43 knockouts.
  • He held the heavyweight title from 1952 to 1956 before walking away from the sport still unbeaten, a feat no other heavyweight champion has matched.
  • This makes Marciano a unique figure in boxing history as the only heavyweight champion to both win and leave the division without ever suffering a defeat.

In short: if the question is “who is the only heavyweight boxing champion to retire with an undefeated record,” the answer is Rocky Marciano.

Information gathered from public forums or data available on the internet and portrayed here.