Reid Flair -- son of wrestling legend Ric Flair -- died from an accidental overdose of heroin and other drugs ... this according to an official autopsy report released today.
As TMZ previously reported ... 25-year-old Flair was pronounced dead on March 29 after his father discovered him out cold in a Charlotte, NC hotel room.
According to the autopsy report ... traces of the muscle relaxant clonazepam and Xanax (anti-anxiety medication) were also found in Reid's system.
Reid -- who had just returned from a wrestling stint in Japan -- had struggled with heroin in the past ... according to several reports, he overdosed 3 times in 2 years.
After the report was released this morning, Ric told the Charlotte Observer, "I loved him ... He should have been on top of the world, but he was fighting a battle he couldn’t win."