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The hard-living screen star died at his home in the coastal Los Angeles suburb of Venice at 8:15 a.m. PDT (1515 GMT), surrounded by family and friends, the friend, Alex Hitz, told Reuters.
In a wildly varied career spanning more than 50 years, Hopper appeared alongside his mentor James Dean in "Rebel Without a Cause" and "Giant" in the 1950s and played maniacs in such films as "Apocalypse Now," "Blue Velvet" and "Speed."
He received two Oscar nominations -- for writing "Easy Rider" (with co-star Peter Fonda and Terry Southern), and for a rare heartwarming turn as an alcoholic high-school basketball coach in the 1986 drama "Hoosiers."
"Easy Rider," regarded is one of the greatest films of American cinema, helped usher in a new era in which the old Hollywood guard was forced to cede power to young filmmakers such as Francis Ford Coppola and Martin Scorsese.
The low-budget blockbuster, originally conceived by Fonda, introduced mainstream moviegoers to pot-smoking, cocaine-dealing, long-haired bikers.
"We'd gone through the whole '60s and nobody had made a film about anybody smoking grass without going out and killing a bunch of nurses," Hopper told Entertainment Weekly in 2005. "I wanted 'Easy Rider' to be a time capsule for people about that period."
Hopper and Fonda were joined on screen by a then-unknown Jack Nicholson as an alcoholic lawyer, but it was not a harmonious set. Hopper clashed violently with everyone and Fonda later described him as a "little fascist freak." Their friendship was destroyed.
Hopper fell ill last September. He continued working almost to the very end, both on his cable TV series "Crash" and on a book showcasing his photography. But his final months were also consumed by a bitter divorce battle with his fifth wife, Victoria Duffy.
Indeed, his private life was never dull. His marriages included an eight-day union in 1970 with Michelle Phillips of the Mamas and Papas, who later told Vanity Fair that she was subjected to "excruciating" treatment.
Hopper is survived by four children.