Angelo Dundee, the renowned trainer who guided Muhammad Aliand Sugar Ray Leonard to boxing glory, died on Wednesday in Clearwater, Fla. He was 90.

His death was announced by his son-in-law, James Coughlin, who said Dundee had recently been treated for blood clots.

In more than 60 years in professional boxing, Dundee gained acclaim as a brilliant cornerman, whether healing cuts, inspiring his fighters to battle on when they seemed to be reeling, or adjusting strategy between rounds to counter an opponent’s style.

“In that one minute, Angelo is Godzilla and Superman rolled into one,” Dr. Ferdie Pacheco, who often worked with Dundee and then became a TV boxing analyst, once remarked.

Ali told The New York Times in 1981: “You come back to the corner and he’ll say, ‘The guy’s open for a hook,’ or this or that. ” If he tells you something during a fight, you can believe it. As a cornerman, Angelo is the best in the world.”

When Thomas Hearns was rallying against Leonard in their welterweight championship unification fight in September 1981, Dundee got Leonard going again after the 12th round bell, telling him, “You’re blowing it, son, you’re blowing it.” Leonard knocked Hearns down in the 13th round and won the bout when the referee stopped it in the 14th.

Dundee “knew precisely how to get through to me at the most pivotal moments, and no moment in the fight, or in my career, was as pivotal as this,” Leonard recalled in his memoir “The Big Fight” (2011),” written with Michael Arkush.

Dundee’s first champion was Carmen Basilio, the welterweight and middleweight titleholder of the 1950s from upstate New York. Although best remembered for Ali and Leonard, Dundee also trained the light-heavyweight champion Willie Pastrano, the heavyweight titleholder Jimmy Ellis and the welterweight champion Luis Rodriguez. Dundee advised George Foreman when he regained the heavyweight title at age 45. He was inducted into the International Boxing Hall of Fame in 1992.

He was born Angelo Mirena in Philadelphia, the son of a railroad worker. He became Angelo Dundee after his brother, Joe, fought professionally under the name Johnny Dundee, in tribute to a former featherweight champion; another brother, Chris, also adopted the Dundee name.

After working as a cornerman at military boxing tournaments in England while in the Army Air Forces during World War II, Dundee served an apprenticeship at Stillman’s Gym near the old Madison Square Garden, learning his craft from veteran trainers like Ray Arcel, Charley Goldman and Chickie Ferrara. In the early 1950s he teamed with his brother Chris to open the Fifth Street gym in Miami Beach. It became their longtime base, Angelo as a trainer and Chris as a promoter.

In the late 1950s, Dundee gave some tips to a promising amateur named Cassius Clay, and in December 1960, after Clay’s first pro bout, Dundee became his trainer, working with him in Miami Beach. He guided him to the heavyweight title with a knockout of Sonny Liston in February 1964.

Dundee avoided the temptation to tamper with the brilliance of his young and charismatic fighter, and he used a bit of psychology in honing his talents.

“I never touched that natural stuff with him,” Dundee recalled in his memoir, “My View From the Corner” (2008), written with Bert Randolph Sugar. He added: “So every now and then I’d subtly suggest some move or other to him, couching it as if it were something he was already doing. I’d say something like: ‘You’re getting that jab down real good. You’re bending your knees now and you’re putting a lot of snap into it.’ Now, he had never thrown a jab, but it was a way of letting him think it was his idea, his innovation.”

When Cassius Clay became Muhammad Ali soon after winning the heavyweight title, his boxing management and financial affairs were handled by the Nation of Islam. Dundee was the only white man in his camp, and he grew disturbed over references to that fact.

In his memoir, Dundee said that he and Ali “had this special thing, a unique blend, a chemistry.”

“I never heard anything resembling a racist comment leave his mouth,” he said. “There was never a black-white divide.”

Dundee knew all the tricks in the boxing trade, and then some.

When Ali — or Clay, as he was still known at the time — sought to regain his senses after being knocked down by Henry Cooper in the fourth round of their June 1963 bout, Dundee stuck his finger in a small slit that had opened in one of Ali’s gloves, making the damage worse. Then he brought the badly damaged glove to the referee’s attention. Dundee was told that a substitute glove wasn’t available, and the few seconds of delay helped Clay recover. He knocked Cooper out in the fifth round.

In the hours before Ali fought Foreman in Zaire in 1974 — the Rumble in the Jungle — Dundee noticed that the ring ropes were sagging in the high humidity. He used a razor blade to cut and refit them so they were tight, enabling Ali to bounce off them when Foreman unleashed his “anywhere” punches from all angles. Ali wore Foreman out, hanging back with the “rope a dope” strategy Ali undertook on his own, and he went on to win the bout.

Dundee became Leonard’s manager and cornerman when he turned pro in 1977. He taught Leonard to snap his left jab rather than paw with it and guided him to the welterweight championship with a knockout of Wilfred Benitez in 1979.

Roberto Duran captured Leonard’s title on a decision in June 1980, but Leonard won the rematch in November when Dundee persuaded him to avoid a slugfest and instead keep Duran turning while slipping his jabs. A thoroughly beaten Duran quit in the eighth round, uttering his inglorious “no mas.”

In talking about his boxing savvy, Dundee liked to say, “When I see things through my eyes, I see things.”

“When Dundee speaks, traditional English usage is, to say the least, stretched and malapropisms abound,” Ronald K. Fried wrote in “Cornermen: Great Boxing Trainers.”

“Yet the language is utterly original and Dundee’s own — and it conveys exactly what Dundee knows in his heart.”

After retiring from full-time training, Dundee had stints in boxing broadcasting. He taught boxing technique to Russell Crowe for his role as the 1930s heavyweight champion Jimmy Braddock in the 2005 movie “Cinderella Man.”

He flew to Louisville last month for a celebration of Ali’s 70th birthday.

Dundee had been living in Palm Harbor, Fla. His survivors include his daughter, Terri Dundee Coughlin; his son, Jimmy; six grandchildren and one great-grandchild. His wife, Helen, died in 2010.

Dundee once remarked: “I’m not star quality. The fighter is the star.”

But he took pride in his craft. As he put it: “You’ve got to combine certain qualities belonging to a doctor, an engineer, a psychologist and sometimes an actor, in addition to knowing your specific art well. There are more sides to being a trainer than those found on a Rubik’s Cube.”

Angelo Mirena Jr