Bruno Sammartino, foreground, wrestling Ivan Koloff. (George Napolitano/MediaPunch/IPx/AP)

Bruno Sammartino fled to the mountains of Italy with his family during World War II and came to the United States at 14, weighing just 80 pounds. Within 10 years, he built himself into a 275-pound mound of muscle, with remarkable strength and a relentless, blue-collar style that made him one of the most popular professional wrestlers of the 1960s and 1970s.

Mr. Sammartino, who was once among the highest-paid athletes in the United States, died April 18 at a hospital in Pittsburgh. He was 82.

The death was confirmed by a family friend, Christopher Cruise, who said he did not know the exact cause.

Mr. Sammartino, who narrowly missed making the U.S. Olympic team as a weightlifter and rejected an opportunity to try out for the Pittsburgh Steelers, settled instead for the rowdy but remunerative world of professional wrestling.

He began his career when wrestling still maintained the pretense of a quasi-legitimate sport and was not the madcap spectacle it would later become. Mr. Sammartino was all business when he entered the ring, wearing trunks and lace-up boots. He had disdain for some of his more colorful counterparts, who wore costumes and depended more on theatrics than athleticism.

“I complained about the gimmicks,” he told The Washington Post in 1980. “All the nonsense and garbage. After a while I just said I would not wrestle with the guys wearing masks, or guys that had some get-up on. It was demeaning. I refuse to go onto the mat against a Christmas tree.”

Bruno Sammartino, with a painting of himself as a wrestler, in 2000. (Gene J. Puskar/AP)

Wrestling fans, particularly in his home town of Pittsburgh, soon adopted Mr. Sammartino as the embodiment of immigrant pluck and blue-collar grit. In a business of loudmouths, sadistic giants and outright cheats, he was the lunch-bucket guy who played by the rules (such as they were) and always got the job done.

“He was the most-loved wrestler in the Northeast,” Dave Meltzer, editor of Wrestling Observer, a newsletter, said in an interview. “He was a product of his time and place. People saw him as real.”

If anyone doubted Mr. Sammartino’s ability or good nature, he made clear that he was not to be fooled with. In one of his first bouts in 1960, he lifted one of his costumed opponents — Haystacks Calhoun, a bearded, 600-pound country lad in bib overalls — and dropped him to the floor.

When he met “Nature Boy” Buddy Rogers in 1963 in the center of the ring for what was then the World Wide Wrestling Federation (now WWE) championship, Mr. Sammartino told the reigning champ that the match would be on the level, that he wasn’t following any script.

Mr. Sammartino locked Rogers in bear hug, then hoisted him on his shoulder in a signature hold called the pendulum backbreaker. “I told him to give up or I was really going to break his back,” Mr. Sammartino said.

The match was over in less than a minute.

Mr. Sammartino remained wrestling’s champion until 1971, defeating such rivals as Killer Kowalski, Professor Toru Tanaka, Gorilla Monsoon and George “The Animal” Steele.

After losing his title to Ivan Koloff, Mr. Sammartino regained the belt in 1973 and held it until 1977, when he yielded to Superstar Billy Graham. His total championship reign of more than 11 years is the longest in pro wrestling history. His fans called him “the Living Legend.”

As wrestling’s biggest star, he earned hundreds of thousands of dollars a year, easily on a par with the highest-paid professional baseball and football players of the time. He appeared at New York’s Madison Square Garden more than 200 times and wrestled in matches all over the world.

But his fame and drawing power could not protect Mr. Sammartino from the dangers and physical toll of wrestling.

In 1976, he was seriously injured in a match with Stan Han­sen, who botched a body slam and dropped Mr. Sammartino on his head, breaking his neck. Mr. Sammartino continued the bout for 15 minutes, only to learn later from his doctor that he could easily have been paralyzed.

After months of recovery, Mr. Sammartino met Hansen again in a series of matches that were top box-office successes. He had other feuds with “Rowdy” Roddy Piper, “Macho Man” Randy Savage and onetime protege Larry Zbyszko before retiring from the ring in 1981.

“You ask if wrestling is for real,” he told The Post in 1980. “Well, I think my own body answers that question. I have broken more bones than any of the others — my neck, collarbone, both arms, wrists, knuckles, all of my ribs, my back. A hairline fracture of the kneecap. My jaw has been wired and rewired. It’s incredible to think people would fake that.”

Bruno Leopoldo Francesco Sammartino was born Oct. 6, 1935, in Pizzoferrato, Italy. He stayed behind in Italy with his mother and siblings after his father moved to Pittsburgh to work in mines and steel mills.

During World War II, German forces took over the Sammartinos’ home town.

“The entire village fled to the mountains, and we lived there for eight months,” Mr. Sammartino told The Post. “It was winter, and there was no food. We ate the snow.”

After the war, he suffered from pneumonia, and his mother nursed him back to health, using leeches to suck toxins out of his body. When he came to the United States in 1950 — and met his father for the first time — he weighed 80 pounds.

He began to lift weights as a way to build up his body and overcome bullying. He played football in high school and reportedly just missed being named to the U.S. Olympic weightlifting team in 1956. He worked in construction while gaining local renown for his feats of strength. In 1959, he set a world record by bench-pressing 565 pounds.

The Steelers asked Mr. Sammartino to try out for the team, but when he learned that National Football League salaries were only about $8,000 a year, he chose professional wrestling instead, beginning his career in 1959.

Over the years, Mr. Sammartino often feuded with the promoters who controlled wrestling, most notably Vincent McMahon Sr., the founder of what is now the WWE.

In the 1980s, Mr. Sammartino occasionally appeared in tag-team matches with a son, David Sammartino. They later became estranged, in part because of reports of the son’s use of steroids.

In retirement, Mr. Sammartino lamented the widespread use of drugs and steroids in pro wrestling, shoddy medical care and growing vulgarity. His only leverage was to refuse invitations to be named to the WWE’s hall of fame.

“I was embarrassed to be associated with it,” he told the Pittsburgh Post-Gazette in 2010. “If I would have accepted induction, I would have been the biggest hypocrite in the world.”

After reassurances that wrestling was cleaning up its practices, Mr. Sammartino agreed to join the hall of fame in 2013.

Survivors include his wife since 1959, the former Carol Teyssier of Pittsburgh; three sons; and four grandchildren.

Away from wrestling, Mr. Sammartino was known as a thoughtful, cultured man who had a deep love of opera. “Franco Corelli is my favorite tenor,” he told The Post.

Just before Corelli was to perform at New York’s Metropolitan Opera, Mr. Sammartino said, “somebody threatened to break both his legs. So he called me up. Would I be his bodyguard, he asked me.”

Mr. Sammartino and two burly friends accompanied Corelli from his apartment to his dressing room.

“I sat nearby during the performance,” he added, “then took him home afterward. Nothing happened, but I was honored.”