Mike Tyson won 19 consecutive professional fights by knockout.
Tyson’s professional debut came on March 6, 1985, when he stopped Hector Mercedes in the first round. He then built a remarkable 19–0 start, ending every bout inside the distance. Twelve of those first 19 victories came in the opening round, helping create his early reputation as one of boxing’s most destructive heavyweights.
In boxing records, “knockout” is often used broadly for both a KO and a technical knockout (TKO). Several of Tyson’s early wins were officially TKOs, including victories over Don Halpin, Jesse Ferguson and Mike Jameson. His 19th opponent, Steve Zouski, was stopped by a conventional third-round KO on March 10, 1986.
The streak ended in Tyson’s next fight. James Tillis lasted all 10 rounds on May 3, 1986, and lost by unanimous decision, making Tyson’s opening run 19 straight stoppage wins rather than 20. Tyson eventually became the youngest heavyweight champion in history when he defeated Trevor Berbick in November 1986.