Legacy thumb|Marciano and Joe DiMaggio visiting President Dwight D. Eisenhower at the White House in 1953 Marciano holds the record with heavyweight Brian Nielsen for the longest undefeated streak by a heavyweight. He is also the only world heavyweight champion to go undefeated throughout his professional career. Although heavyweight champion Gene Tunney never suffered a defeat at heavyweight and retired as champion, he lost one career fight at light heavyweight, and his longest win streak was 32, with his overall record being 82-1-4(D)-1(NC). Marciano also has the highest knockout percentage of any heavyweight champion in history (over the period of a career) with 87.76%. In his professional career, he was only knocked down twice. The first occurred in his first title fight against Jersey Joe Walcott, and the second occurred against Archie Moore.
Legacy thumb|Marciano and Joe DiMaggio visiting President Dwight D. Eisenhower at the White House in 1953 Marciano holds the record with heavyweight Brian Nielsen for the longest undefeated streak by a heavyweight. He is also the only world heavyweight champion to go undefeated throughout his professional career. Although heavyweight champion Gene Tunney never suffered a defeat at heavyweight and retired as champion, he lost one career fight at light heavyweight, and his longest win streak was 32, with his overall record being 82-1-4(D)-1(NC). Marciano also has the highest knockout percentage of any heavyweight champion in history (over the period of a career) with 87.76%. In his professional career, he was only knocked down twice. The first occurred in his first title fight against Jersey Joe Walcott, and the second occurred against Archie Moore.