Matthew Saad Muhammad, a former light heavyweight boxing champion who was abandoned as a child and went on to become one of the most exciting boxers of the 1970s and 1980s, died May 25 at a Philadelphia hospital. He was 59.

Kevin Roberts of the nonprofit Resources for Human Development, for which Mr. Saad Muhammad worked as an advocate for the homeless, confirmed the death. Roberts told the New York Times that Mr. Saad Muhammad had amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease.

During his 18-year boxing career, Mr. Saad Muhammad was known as a thrilling and determined fighter who had the ability to bounce back after absorbing considerable punishment from his opponents.

In 1979, he fought veteran Marvin Johnson for the World Boxing Council’s light heavyweight (175 pounds) crown. Despite cuts above both eyes, Mr. Saad Muhammad won on a technical knockout in an action-packed eighth round.

Mr. Saad Muhammad’s 1980 title defense against Mexican boxer Alvaro “Yaqui” Lopez was named “Fight of the Year” by Ring magazine, with the eighth round named one of the greatest in history.

Matthew Saad Muhammad holds up his light heavyweight title belt in November 1980 as he is carried around the ring after knocking out challenger Lotie Mwale in their title fight in San Diego. (File/AP)

During his bout with Lopez, Mr. Saad Muhammad refused to go down, despite taking as many as 70 unanswered blows in the eighth round. He rallied later in the fight and went on to win by TKO in the 14th round, inspiring his nickname, “Miracle Matthew.”

Mr. Saad Muhammad defended his world title eight times, seven of them by knockout, before losing in December 1981 to Dwight Muhammad Qawi on a 10th-round TKO.

Mr. Saad Muhammad continued to box until 1992, retiring with a 49-16-3 record that included 35 knockouts. He was inducted into the International Boxing Hall of Fame in 1998.

“Matthew Saad Muhammad was one of the most exciting boxers of all time. His drama-filled fights were thrilling and he was a real fan favorite,” the Hall of Fame’s executive director, Edward Brophy, said in a statement.

Mr. Saad Muhammad was born June 16, 1954 in Philadelphia as Maxwell Antonio Loach. After his mother died when he was 5, he was taken in by an aunt.

The police soon found him abandoned on a highway and took him to a Catholic social services agency. The nuns gave him the first name Matthew and the last name of Franklin, after the parkway on which he was found.

“(My brother) took me out in the city, where I wouldn’t know where I was or how to find my way home, and ran away from me,” Mr. Saad Muhammad told One Step Away, a newspaper produced by residents of city shelters, this year. “I tried to run after him. I ran as fast as I could. I was 5 years old and I was running for my life.”

He began boxing professionally in 1974 as Matthew Franklin before changing his name after converting to Islam.

Mr. Saad Muhammad became homeless in his 50s and lived for a time in a city shelter. He later became a spokesman for One Step Away’s “Knock Out Homelessness.”

Information about survivors could not be confirmed.

— News services and staff reports