Rodney King, the African-American at the centre of the Los Angeles riots 20 years ago, has been found dead aged 47.
His fiancee discovered his body at the bottom of a swimming pool, but there was no sign of foul play.
King was a victim of police brutality in 1991, but the officers involved were acquitted the following year.
The verdict triggered clashes between rioters and police which left more than 50 dead, thousands injured and thousands of properties destroyed.
Police said on Sunday that King had been found "unresponsive" at the bottom of his pool in Rialto, a city in San Bernardino County, just west of Los Angeles.
He was pronounced dead at 06:11 (13:11 GMT) on Sunday, said Police Captain Randy Deanda.
Rodney King's beating at the hands of the police, which left him with brain damage, was filmed by a bystander and shown by media outlets across the world.
He had been stopped for speeding on a dark street on 3 March 1991. The four LA police officers who pulled him over hit him more than 50 times with their batons, kicked him and shot him with stun guns.
The BBC's Alastair Leithead in Los Angeles says the iconic images of his beating had a huge impact at the time on an already tense Los Angeles.
Eventually, the whole chain of events had a profound impact on the way race was dealt with in the US, our correspondent says.
King recently told the Los Angeles Times that while he had come to terms with his broader legacy, dealing with the past had not been easy.
"I sometimes feel like I'm caught in a vise," he said. "Some people feel like I'm some kind of hero. Others hate me. They say I deserved it. Other people, I can hear them mocking me for when I called for an end to the destruction, like I'm a fool for believing in peace."
A later trial resulted in two of the four officers being jailed. King sued the City of Los Angeles and won $3.8m (£2.5m) compensation.
The rioting that gripped LA in the wake of the original not-guilty verdict went on for days, leaving 50 people dead and causing $1bn of damage to the city.
King went on television three days into the rioting to call for calm, pleading that everyone "just get along" - years later he said he wanted that statement to be his legacy.
The Los Angeles Police Department itself was forced to change in the wake of the Rodney King case, which highlighted widespread racism in the largely white, male force.
It was not uncommon for officers to describe African-Americans as "monkeys" and "gorillas", and some police bragged about beating suspects over their patrol car radios.
An independent commission was set up to investigate the issue, chaired by future US Secretary of State Warren Christopher.
It recommended boosting multiculturalism in the police force and the LAPD had slowly shifted to a more community-focused style of policing.
As for Rodney King himself, he got engaged to one of the jurors from his trial and published a book in 2012 titled The Riot Within: My Journey From Rebellion to Redemption.
But he also struggled with drug and alcohol abuse and had several brushes with the law over the years, and he eventually lost all his money.
The Los Angeles Police Department said that at this time it had no comment to make on the death of King, adding that the death had occurred in Rialto, out of its jurisdiction.