Ken Norton, who had three memorable fights with Muhammad Ali, breaking Ali’s jaw in winning their first bout, then losing twice, and who went on to become the World Boxing Council heavyweight champion, died Wednesday in the Las Vegas suburb of Henderson, Nev. He was 70.

His death was confirmed by his son Ken Jr., an assistant coach with the Seattle Seahawks of the N.F.L. and a pro linebacker for 13 seasons, The Associated Press said. Norton had been in poor health for several years after sustaining a series of strokes, The A.P. reported.

Norton defeated Ali on a 12-round split decision in 1973 to capture the North American Boxing Federation heavyweight title. Norton was an exceptionally muscular 6 feet 2 inches and 220 pounds, but he was a decided underdog in the first Ali fight.

“Ali thought it would be an easy fight,” Norton’s former manager, Gene Kilroy, was quoted by The A.P. as saying. “But Norton was unorthodox. Instead of jabbing from above like most fighters, he would put his hand down and jab up at Ali.”