Schulberg died of natural causes at his home in Westhampton Beach, on Long Island, said his wife, Betsy Schulberg. He was taken to a nearby medical center, where doctors unsuccessfully tried to revive him, she said.
"He was very loved," she said, "and cherished."
"On the Waterfront," directed by Elia Kazan and filmed in Hoboken, N.J., was released in 1954 to great acclaim and won eight Academy Awards. It included one of cinema's most famous lines, uttered by Brando as the failed boxer Terry Malloy: "I coulda been a contender."
Schulberg never again approached the success of "On the Waterfront," but he continued to write books, teleplays and screenplays - including the Kazan-directed "A Face in the Crowd," and scores of articles. Spike Lee was an admirer, dedicating the entertainment satire "Bamboozled" to Schulberg and working with him on a film about boxer Joe Louis.
Schulberg was first known for the novel "What Makes Sammy Run?" Published in 1941, it follows the shameless adventures of Sammy Glick (born Shmelka Glickstein) as he steals, schmoozes and backstabs his way from office boy at a New York newspaper to production chief at a major Hollywood studio.
Unlike Nathaniel West's "The Day of the Locust," which immortalized the desperation of show business outsiders, Schulberg's book was an insider's account, and Hollywood responded as it would to one of its own: fascinated and betrayed. Everybody from movie executives to columnist Walter Winchell was convinced he or she knew the real-life model for Glick. Schulberg later said he based the character on numerous hustlers he had encountered.
"What I had, when I read through my notebook, was not a single person but a pattern of behavior," he later wrote.
The model for countless Hollywood satires to come, Schulberg's novel was adapted for television, Broadway (a flop musical starring Steve Lawrence), but, ironically, has waited decades to be made into a film. A planned DreamWorks production featuring Ben Stiller was "in development" in recent years.
"I have a feeling they're not going to do it," Schulberg told The Associated Press in 2006. "It's still a little tough for them."
Like Glick, Schulberg had working knowledge of the movie business; he was the son of Paramount studio head B.P. Schulberg. And like the "On the Waterfront" hero Malloy, who testifies about corruption on the docks, Schulberg informed on his peers.
In 1951, he named names as he acknowledged a communist past before the House Un-American Activities Committee, becoming one of Hollywood's most prominent witnesses. He appeared voluntarily to acknowledge he had been a communist from 1936 to 1939. He claimed he was disillusioned by Stalin's nonaggression pact with Hitler and quit the party when it tried to make him write "What Makes Sammy Run?" with a Marxist twist.
In 2003, Schulberg was voted into the International Boxing Hall of Fame as an "observer," a category established the previous year for journalists and historians. In his later years, he worked on a memoir, drawing upon correspondence with Robert Kennedy, F. Scott Fitzgerald and others.
He was a supporter of Kennedy's 1968 presidential campaign and was among the last to speak with the Democratic candidate before he was assassinated in Los Angeles.
Schulberg remained active in his 90s, collaborating in 2008 on a stage version of "On the Waterfront" presented at the famous Fringe arts festival in Edinburgh, Scotland. He told The New York Times that he always felt Brando's character should realistically have been killed in the end for testifying against organized crime. But the director of the festival play stuck with a happy ending, just as Kazan had done a half-century earlier, Schulberg said.
Schulberg's prose was scrappy and streetwise, but the streets of his childhood were well paved. Born in New York City, he grew up in Hollywood and remembered riding in a fancy Lincoln town car, complete with gold wicker and carriage lights.
"I hated that car so much that when I had to be driven to school in it I would lie on the floor and crawl out a block away so my school mates wouldn't see my shame," he recalled years later.
He went East to be educated at Deerfield Academy and Dartmouth but returned to Hollywood to work in movies, describing himself as an underworked $25-a-week "reader, junior writer and utility outfielder."
"I passed the time writing short stories," he said, and his first six efforts, including a tale titled "What Makes Sammy Run," were bought by leading national magazines.
He then isolated himself in Vermont and expanded the story into a novel. Despite a modest first printing, the book was a huge success and was widely praised.
"A biting but nonvicious appraisal of Hollywood," wrote the New York World-Telegram. Dorothy Parker and Damon Runyon were also admirers.
But, inevitably, Schulberg made enemies. Samuel Goldwyn fired him, and Louis B. Mayer, head of MGM, said Schulberg should be "deported." John Wayne feuded with him for decades.
Some Jews were concerned that Glick would reinforce negative stereotypes. But Schulberg responded that many of Glick's victims were Jewish and noted a supportive quote from Parker: "Those who hail us Jews as brothers must allow us to have our villains, the same, alas, as any other race."
In later years, Schulberg was dismayed when young people cited Glick as a role model.
"I grew up hating him," he said. "Now I'm being made to feel as if I'd written a how-to book: 'How to Succeed in Business While Really Trying."'
During World War II, Schulberg spent 3 1/2 years in Washington and Europe on duty with the Office of Strategic Services, forerunner of the CIA. All the while, he wrote short stories.
In 1947, he published "The Harder They Fall," a fictionalized expose of boxing, a sport he remained close to all his life; he wrote newspaper columns on it in later years. The 1955 screen version of "The Harder They Fall," which Schulberg also wrote, was Humphrey Bogart's last movie.