Rodney King, whose 1991 beating at the hands of police led to deadly riots in Los Angeles the following year, was found dead in a swimming pool today in Rialto, California, police said.
Mr King, 47, whose beating was captured on video by a bystander, was discovered by his fiancee, Rialto police Captain Randy De Anda said.
Mr King's death was reported to police this morning in Rialto, about 50km east of Los Angeles.
Police pulled his body from the swimming pool but were unable to resuscitate him, Mr De Anda said.
The Rialto police department is conducting a drowning investigation and Mr De Anda said there were no preliminary signs of foul play.
Mr King became a national figure in discussions on race and police brutality after he and some friends were stopped by Los Angeles police on 3 March 1991, after a high-speed chase.
Mr King was beaten by baton-wielding officers while a bystander filmed them.
When the officers were cleared of brutality charges, riots broke out in Los Angeles, resulting in 53 deaths and an estimated $1bn in damage.