Jake LaMotta, right, fights Marcel Cerdan in Briggs Stadium in Detroit in 1949. (AP/AP)

Jake LaMotta, an iron-jawed boxer who brawled his way to the world middleweight championship in 1949 and whose tempestuous life was compellingly portrayed in an Oscar-winning performance by Robert De Niro in the film “Raging Bull,” died Sept. 19 at a rehabilitation facility in Aventura, Fla.

He was 95, according to his family, although some records indicate he may have been a year older. A daughter, Christi LaMotta, announced his death in a Facebook post but did not provide additional details.

Even by the standards of boxing, Mr. LaMotta was a rough-hewn specimen, a product of the New York slums who learned his brutal trade on street corners and in reform school. Brash and glib, ruggedly handsome and charismatic in a dark, dangerous way, he was one of the leading fighters of the 1940s and early ’50s, when boxing was among the nation’s most popular sports.

He wore a hooded leopard-print robe into the ring and fought with a stubborn, inelegant fury that led him to be called the Bronx Bull. He stalked forward in the ring, with “blows bouncing off him like ball bearings off a battleship,” as Associated Press sportswriter Whitney Martin put it, absorbing punches and pain like few fighters before or since.

He was a burly, compact 5-foot-8 and fought in a low crouch, attacking his opponent’s body in a swarming, relentless style, launching blunt-force punches­ that seemed to rise from the canvas.

Newly crowned world middleweight boxing champion Jake LaMotta with wife Vikki in 1949. (AP)

“To LaMotta, fighting was a personal statement,” author and historian Bert Sugar wrote in his 2006 book “Boxing’s Greatest Fighters.” “He fought with an anger that seemed as if it would spring forth from the top of his head like a volcanic eruption.”

Even when he lost, with his features bloodied and bruised, Mr. LaMotta retained a measure of pride by refusing to go down. The Ring magazine, the leading boxing periodical, said he had the “toughest chin” in the sport’s history.

“The truth of the matter?” Mr. LaMotta told the Chicago Sun-Times in 1996. “The punches never hurt me. My nose was broken six times, my hands six times, a few fractured ribs. Fifty stitches over my eyes. But the only place I got hurt was out of the ring.”

For years, Mr. LaMotta refused to cooperate with the mobsters who controlled boxing when he was in his prime. Although he was a top-ranked contender, he was not granted a chance to fight for the championship until after he agreed to play along with the gangsters.

He deliberately lost a fight in 1947 — benefiting the gamblers who bet against him — and was suspended for several months because his lackluster effort was so blatantly obvious.

Two years later, he got his title shot, defeating Marcel Cerdan, an Algerian-born French boxer who was known, among other things, for having an affair with the singer Edith Piaf. Cerdan injured his shoulder in the first round and gave up at the beginning of the 10th round, giving Mr. LaMotta the championship.

Later in 1949, while flying back to the United States to face Mr. LaMotta in a rematch, Cerdan was killed in an airplane crash. Mr. LaMotta defended his middleweight crown against two other boxers — and had four other nontitle fights — before entering the ring one last time against Sugar Ray Robinson, his longtime rival.

Between 1942 and 1945, the two boxers had met five times. (Years later, when he had a nightclub act, Mr. LaMotta joked, “I fought Sugar Ray Robinson so many times, it’s a wonder I didn’t get diabetes.”)

Mr. LaMotta drove Robinson through the ropes of the ring in their second match, in 1943, giving Robinson his first loss in a professional fight. Robinson won the world welterweight (147 pound) championship in 1946, and many boxing historians rank him as the greatest boxer in the history of the sport. His battles with Mr. LaMotta were often close and always entertaining.

On Feb. 14, 1951, when they met in Chicago, Mr. LaMotta was weakened from having to lose almost five pounds in 12 hours to make the 160-pound weight limit. For the only time in his career, he later admitted, he took a couple of swigs of brandy before climbing through the ropes.

“The brandy wasn’t to give me strength,” he admitted in his 1970 autobiography. “It was to give me false courage. And what false courage is really is true fear.”

The crowd cheered wildly throughout the fight, which was shown on national television. Mr. LaMotta battled gamely, but he was exhausted after an 11th-round flurry failed to put Robinson on the floor. In the 13th round, Robinson pummeled Mr. LaMotta at will before the referee stopped the fight, making Robinson the new champion.

“The finish found a pulp-faced, vacant-eyed Jake LaMotta backed to the ropes and holding on — but still on his feet,” a Time magazine writer noted.

The bout became forever known in boxing circles as the “St. Valentine’s Day Massacre,” and it was the first step in a long slide to oblivion for Mr. LaMotta.

After moving to the light-heavyweight division, he was knocked down in 1952 for the first and only time in his career. Two years later, he retired from boxing with a record of 83 wins, 19 losses, 4 draws.

After opening a nightclub in Miami Beach, Mr. LaMotta went to jail in 1957 for enabling the prostitution of a minor, when a 14-year-old girl was arrested in his bar. He served time on a chain gang and was placed in solitary confinement, where he broke his hands punching a wall.

In 1970, he and two co-writers published a memoir, “Raging Bull,” which describes his boxing career and casts a searching light into his soul.

“Besides being a slum kid with no great education in anything except how to fight and stay alive and steal, I also had this temper,” Mr. LaMotta wrote in “Raging Bull.” “Everybody has a temper, but mine was set on a hair trigger.”

He sent a copy of the book to De Niro, then a young actor, who eventually interested director Martin Scorsese in a movie project. Before filming began, De Niro spent a solid year training with Mr. LaMotta in the boxing ring, sparring more than 1,000 rounds with each other.

“I swear, without exaggeration,” Mr. LaMotta said in 2005, “when I got done with him he could have fought professionally. That’s how dedicated he was.”

In the film, De Niro mimicked Mr. LaMotta’s crouching style in the fight scenes and also captured the suspicion, anger and violence that Mr. LaMotta often directed toward his friends and family, particularly his wife at the time, Vikki.

Mr. LaMotta and Vikki saw the film together before it was released in 1980.

“After the movie, I said, ‘Gee, they made me look bad,’ ” he recalled in 2001. “ ‘Was I that bad?’ And she said, ‘You were worse.’ ”

Mr. LaMotta complained that “Raging Bull” was “a very negative movie” and that, among other things, he didn’t use profanity nearly as much as De Niro did in the film. But, as he told the New York Daily News in 2000, “the picture they portrayed is pretty accurate. I would say it’s about 90 percent truth.”

He was present at the Dorothy Chandler Pavilion in Los Angeles in 1981 when De Niro won an Academy Award as best actor. Mr. LaMotta then went on to a long second career as the “Aging Bull,” delivering one-liners, signing autographs and making appearances before far more people than ever attended his fights.

Without the film, he told The Washington Post in 1997, “I’d be in bad shape. It made me champ all over again.”

Giacobbe LaMotta was born on the Lower East Side of Manhattan and grew up in the Bronx. Boxing records indicate that he was born July 10, 1921, but his family said he was born a year later.

At 15, Mr. LaMotta was sent to reform school for attempted burglary. He was relieved that he wasn’t arrested on more serious charges after he struck a bookmaker over the head with a lead pipe, took his money and left him for dead.

Mr. LaMotta soon took up boxing in earnest and had his first professional fight at 19. Seven years later, realizing he could not get a chance at the title without working with mobsters, he agreed to “throw” a fight against a boxer named Billy Fox. The referee halted the bout when Mr. LaMotta didn’t attempt to block any punches, but his tactics were so obvious that his boxing license was temporarily suspended.

In 1960, Mr. LaMotta was summoned before a Senate committee investigating racketeering in boxing and freely admitted what he had done. Warned that he might be killed for testifying against underworld figures, he replied, “I’m not afraid of none of them rats.”

Like many former boxers, Mr. LaMotta had trouble adjusting to life after the ring. He played a bartender in the 1961 Paul Newman-Jackie Gleason movie about pool sharks, “The Hustler,” and held jobs as a garbage collector, strip-club bouncer and stand-up comedian. He was inducted into the International Boxing Hall of Fame in 1990.

Mr. LaMotta was married six times, most memorably to his second wife, Beverly Thailer, who was better known as Vikki and was played by Cathy Moriarty in the film “Raging Bull.”

They were married in 1946, when Vikki was 16. At age 51, she appeared in a nude pictorial in Playboy, prompting a predictable joke from Mr. LaMotta: “She always complained she had nothing to wear. I never believed her until I saw her in Playboy.”

She died in 2005. Their two sons both died in 1998. Mr. LaMotta had five children with other wives. Survivors include his fiancee, Denise Baker, a former actress who had collaborated with him on a cabaret show. A complete list of survivors was not immediately available.

In both his autobiography and the film, Mr. LaMotta was portrayed as a tireless Lothario, a pattern that continued throughout much of his life. During an interview at a restaurant with a Post reporter when he was 75, a much-younger woman approached Mr. LaMotta’s table and pressed a piece of paper with her home address and phone number into his hand.

He shrugged it off, as if it happened every day.