Tony Holden, Morrison's longtime friend and manager, told the Tulsa, Okla., World the ex-fighter died Sunday in a Nebraska hospital. Holden didn't reveal a cause of death.
Morrison first garnered significant attention in 1989 when he was cast to star opposite Sylvester Stallone in "Rocky V."
Morrison claimed the World Boxing Organization heavyweight title on June 7, 1993, with a unanimous decision over George Foreman in Las Vegas. He lost the title four months later in Tulsa on a technical knockout to Michael Bentt.
He was suspended by the Nevada State Athletic Commission in 1996 at age 27 after testing positive for HIV, but vehemently contended the tests were false positives.
Morrison, an Arkansas native, was arrested in Fayetteville in 1999 after police discovered drugs and a gun in his car, and was arrested again only weeks later on charges of marijuana possession and public intoxication, the newspaper reported.
He served a 14-month sentence in an Arkansas prison on those charges.
Morrison finished his career with a 48-3-1 record, including 42 knockouts.