<Tr> <Th> Wins by KO </Th> <Td> 43 </Td> </Tr> <Tr> <Th> Losses </Th> <Td> 0 </Td> </Tr> <P> Rocco Francis Marchegiano (September 1, 1923--August 31, 1969), best known as Rocky Marciano (/ mɑːrsiˈɑːnoʊ /), was an American professional boxer who competed from 1947 to 1955 . He held the world heavyweight title from 1952 to 1956, and is the only world heavyweight champion in professional boxing history to retire undefeated . His six title defenses were against Jersey Joe Walcott, Roland La Starza, Ezzard Charles (twice), Don Cockell and Archie Moore . </P> <P> Known for his relentless fighting style, formidable punching power, stamina and exceptionally durable chin, Marciano has been included by boxing historians in lists of the greatest boxers of all time, and is currently ranked by BoxRec as the 16th greatest heavyweight boxer in history . His knockout - to - win percentage of 87.76 remains one of the highest in heavyweight boxing history . </P>

Who is the only professional boxer to end his career undefeated with a record of 49-0