Marlon Brando, who changed not just the face but the mind and soul of movie acting with a series of revolutionary performances in the 1950s, died Thursday at age 80 of lung failure at UCLA Medical Center in Los Angeles.

In his five decades on screen, Mr. Brando fundamentally altered Hollywood's image of a leading man, bringing out an unprecedented emotional rawness in hard-guy characters such as Stanley Kowalski in A Streetcar Named Desire and Terry Malloy in On the Waterfront, then, improbably, reviving his career a generation later as courtly Mafia don Vito Corleone in The Godfather.

The actor's off-screen life was as tumultuous as any of his characters'. He was married three times, fathered (reportedly) 11 children and became the owner of a Tahitian island, as well as an estate on Mulholland Drive. In 1991, he saw his son Christian convicted and sent to prison for killing the boyfriend of his half-sister, Cheyenne, who later took her own life.

Mr. Brando's attorney, David J. Seeley, said funeral arrangements would be private. If Mr. Brando was anything like the eccentric gunslinger he played in The Missouri Breaks (1976), cremation would be unthinkable. "I'd like almost anythin' better 'n' bein' burnt up," cracked that cross-dressing gunman.

For many fair-weather fans, the Method actor's real agony merged with his personae.

Yet the chaos of his off-screen life never tainted the respect of his fellow artists - he won two Academy Awards - and even seemed to prove the authenticity of his persona as an untamable rebel. The Wild One (1954), his smash-hit biker movie, might not have been his best film, but it gave him a key line. A girl asks him, "What're you rebelling against?" and he responds, "Whaddya got?"

"Walt Whitman transformed the language of poetry, Marlon Brando transformed acting. ... He made it more natural, more sexy, more psychologically alive and dangerous," said Peter Manso, author of a merciless 1994 biography of Mr. Brando.

"Brando has towering importance as an icon," says Mr. Manso. "This was the archetypal rebel. You wouldn't have punk today were it not for Marlon Brando. He's the one that made sex dangerous on the big screen."

Francis Coppola, who directed him in The Godfather, said, "Marlon would hate the idea of people chiming in to give their comments about his death. All I'll say is that it makes me sad he's gone."

Mr. Brando's creation of his signature antisocial persona was all the more amazing because it grew out of an all-American background. He was born in Omaha, Neb., in 1924 and got his first taste of theater at the Omaha Community Playhouse. His father sent him to a military school that expelled him. At age 19, he made his way to New York and studied with Method acting legend Stella Adler.

Broadway revelation

It didn't take long for him to get noticed. His performance in his first Broadway play, Maxwell Anderson's Truckline Cafe (1946), made his reputation. Film critic Pauline Kael was in the audience, and later illuminated Mr. Brando's extraordinary gifts as a stage and screen performer.

"We all know that movie actors often merge with their roles in a way that stage actors don't, quite, but Brando did it even on the stage," Ms. Kael wrote.

" ... I looked up and saw what I thought was an actor having a seizure onstage. Embarrassed for him, I lowered my eyes, and it wasn't until the young man who'd brought me grabbed my arm and said, 'Watch this guy!' that I realized he was acting."

Steve Vineberg, professor of theater at the College of the Holy Cross and the author of Method Actors, expressed the unusual blend of shock and grief that news of the actor's death triggered in stage and screen artists everywhere.

"I thought he'd live forever," Mr. Vineberg said, "maybe because of the immediacy of his performances. They haven't dated a bit. I think he's the greatest of all American actors."

To this day, the cliche idea of a male movie star is that he's someone guys want to be and women want to be with. Mr. Brando was a star for a different reason. When he was in his zone, whether as a boxer in On the Waterfront (1954) or a homosexual Army officer in Reflections in a Golden Eye (1967), you felt that you were him.

Brando biographer and film historian and critic David Thomson said yesterday that Mr. Brando's early success in Streetcar fed the impression that he squandered his talent: "His Stanley in Streetcar was a stunning performance, and he really never did another thing on the stage. That was a huge loss."

Still, the marriage of Mr. Brando and Hollywood was, at first, artistically ecstatic. Mr. Brando swiftly showed his versatility on screen. In his debut movie, The Men, he used all his extraordinary physicality in the role of a paraplegic Word War II veteran, giving his character an aura of checked energy. The trademark hems and haws that began punctuating his dialogue reflected the music of his innermost being.