Jimmy Ellis, right, lands a right hook to the head of Leotis Martin during their 12-round world heavyweight title elimination fight Aug. 5, 1967, in Houston. Ellis won the bout en route to the crown. (Associated Press)

Jimmy Ellis, who beat Jerry Quarry to become World Boxing Association heavyweight champion in 1968 and fought the era’s best fighters, including his friend Muhammad Ali, died May 6 at a hospital in Louisville. He was 74.

His son, Jeff Ellis, confirmed the death. Mr. Ellis had suffered from dementia for more than a decade.

As Ali’s former sparring partner and a fellow Kentuckian, Mr. Ellis was among a group of boxers who traded title belts during one of the heavyweight division’s most celebrated eras. His 15-round majority decision against Quarry in Oakland, Calif., came in the finale of an eight-man tournament in which he also beat Leotis Martin and Oscar Bonavena.

Later that year in Stockholm, Mr. Ellis defended the belt against two-time heavyweight champion Floyd Patterson in another title fight that he won on points.

“I was made out to be nothin’ but a sparring partner,” Mr. Ellis said in a 1968 interview with Sports Illustrated after winning the world title. “It bothered me to be run down like that. I was more than that. I knew it. I think I’ve proven that now.”

Mr. Ellis won the WBA belt that Ali held until he was stripped of his titles for refusing induction into the Army during the Vietnam War. Mr. Ellis, who was 6-foot-1 and 197 pounds when he took the crown, won 40 bouts, 24 by knockouts, and lost 12 in his 14-year professional boxing career.

He was WBA champion until Joe Frazier defeated him in February 1970 at Madison Square Garden in New York. In that fight, Frazier knocked him down twice in the fourth round, and Mr. Ellis didn’t come out of his corner for the fifth.

Mr. Ellis began his boxing career at the Columbia Gym in Louisville, where he was trained by police officer Joe Martin, who was credited with spotting Ali’s talent. Ali and Mr. Ellis later shared the renowned trainer Angelo Dundee.

After losing his world title, Mr. Ellis had unsuccessful bouts with Ron Lyle, Joe Bugner and Frazier before retiring in 1975 after injuring his left eye during training. He later developed a form of dementia that is common to boxers.

James Albert Ellis was born Feb. 24, 1940, in Louisville, the son of a Baptist minister. He was one of nine children.

He had a strong interest in gospel music from his teenage years and was a featured singer in a spiritual group based at the Riverview Baptist Church, where his father became pastor. The group toured and released recordings, even while Mr. Ellis pursued boxing.

Mr. Ellis first encountered Ali, then known as Cassius Clay, from watching him fight on local television in the late 1950s. They often sparred, then became friends.

They met in a North American Boxing Federation championship bout in 1971. While neither fighter was knocked down, the referee stopped the match at 2:10 of the 12th round, awarding a victory to Ali. They remained friends after Mr. Ellis’s retirement from the ring in 1975.

“I still talk to Muhammad once a week on the phone and he never, ever, begins our conversation without the words ‘‘Hi, champ,’’ Mr. Ellis told the London Daily Telegraph in 2003.

In addition to his son Jeff, Mr. Ellis’s survivors include five children and 10 grandchildren. His wife, the former Mary Etta Williams, died in 2006.

— Bloomberg News