Pernell Whitaker, a nimble Virginia boxer known as perhaps the greatest pound-for-pound fighter of his generation and a defensive ring artist whose genius for dodging punches, helped him win an Olympic gold medal and world championships in four weight classes, died July 14 after being hit by a driver in Virginia Beach. He was 55.

Mr. Whitaker was apparently walking near an intersection when he was struck by a vehicle around 10 p.m. Sunday, police said in a statement. The driver remained on the scene, where Mr. Whitaker was pronounced dead. The investigation is ongoing, and police said they did not believe that drugs, alcohol or road speed were factors in the collision.

Nicknamed “Sweet Pea,” Mr. Whitaker was an elusive left-hander who regularly slipped away from his opponents, dancing across the ring en route to a slew of world titles. He became the undisputed lightweight champion after defeating Juan Nazario in 1990 and also won titles as a light welterweight, welterweight and light middleweight.

Mr. Whitaker “was one of the best defensive fighters and pure boxers who ever fought,” said Al Bernstein, a Hall of Fame boxing analyst and commentator. At one 10-round fight, he recalled by phone, Mr. Whitaker’s opponent landed only 10 punches — “the kind of number you could never imagine seeing.”

“People always ask what would happen if Whitaker and Floyd Mayweather Jr. fought,” he added, referring to the champion boxer who inherited Mr. Whitaker’s reputation for defensive brilliance. “Probably the answer is no one would land a punch.”

Mr. Whitaker retired in 2001 with a professional record of 40-4-1, including 17 knockouts and three highly controversial decisions: a 1988 loss to José Luis Ramírez in France, a 1993 draw against Julio César Chávez in San Antonio and a 1997 loss to Oscar De La Hoya in Las Vegas. In the eyes of many boxing analysts, he was robbed each time.

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He later worked as a trainer in Virginia Beach — guiding boxers such as Calvin Brock and Zab Judah — amid struggles with cocaine and alcohol that sometimes landed him in jail. In 2007, he was inducted into the International Boxing Hall of Fame in Canastota, N.Y., which praised the “stinging right jab and straight left hand” that helped him defeat foes including Azumah Nelson, Buddy McGirt, Jorge Páez and Harold Brazier.

Raised in a Norfolk public-housing project, Mr. Whitaker parried and punched his way to stardom at 20, when he dominated the lightweight division at the 1984 Olympics in Los Angeles. One of nine American boxers to win a gold medal at the Games, he was described by fellow Olympian Evander Holyfield as the most promising of the bunch.

“He’s a sneaky guy, in a nice way, and he boxes sneaky,” Holyfield told the New York Times. “He’ll throw his arm out, and if you flinch, he probably won’t throw a punch. But if you don’t flinch, he might pop you.”

Mr. Whitaker turned pro later that year with a bout at Madison Square Garden. In 1989, he was named fighter of the year by the Ring magazine and defeated Greg Haugen to win his first lightweight world title. “I couldn’t get no punches off,” Haugen said, offering a complaint that was echoed by fighters for the next decade.

In search of new competition, Mr. Whitaker ranged beyond his original weight class, taking on Chávez in 1993 when the Mexican boxer was considered one of the world’s greatest fighters, undefeated after 87 bouts. Slipping, weaving and darting before a crowd of more than 63,000 at the Alamodome, the fight was often cited as Mr. Whitaker’s finest night in the ring.

But while most sportswriters named Mr. Whitaker the victor, the judges ruled differently, with one calling it in his favor and the other two deeming it a draw. The resulting tie, wrote Sports Illustrated journalist William Nack, was a decision that was “violently in contempt of plausibility.” Mr. Whitaker appeared on the magazine’s cover above a one-word headline: “Robbed!”

“I put an old-fashioned project beating on him,” Mr. Whitaker said the morning after the fight, with characteristic bravado. “A housing authority beating. A ghetto beating. Everyone tried to build him up, but I condemned the building. Pound for pound, Pernell Whitaker is the best fighter in the world. I’m not just a runner; I can fight. Give me credit. Give me the respect I deserve. Give me this one!”

Mr. Whitaker was born in Norfolk on Jan. 2, 1964, and rarely discussed his upbringing, saying that he grew up as a street fighter and began boxing at 8. Pete, as he was known, entered national tournaments and went 201-14 as an amateur, winning events including the 1983 Pan American Games. He was said to have acquired the nickname “Sweet Pea” after a reporter misheard his friends calling him “Sweet Pete” at a boxing match.

In 1985, he married Rovanda Anthony at a ringside ceremony in Virginia Beach, after a card featuring four other Olympic medalists. (Mr. Whitaker was sidelined from the event with a broken foot.) Their marriage ended in divorce, according to promoter Kathy Duva, who worked with Mr. Whitaker in recent years.

Mr. Whitaker had four children from his marriage (he is predeceased by a son) and a daughter from an earlier relationship. Complete information on survivors was not immediately available.

Backed by trainers George Benton and Lou Duva, Mr. Whitaker challenged Ramírez for his first world title in 1988, losing on a split decision before winning a rematch the next year. He later signed a lucrative television contract with HBO but by the late 1990s was struggling to dispatch opponents he had once dominated with ease.

A 1997 win was overturned after he tested positive for cocaine, and in two of his final bouts he suffered a fractured jaw and a broken clavicle that effectively ended his career.

In 2003, he was sentenced to 27 months in prison for repeated probation violations, including for bringing cocaine to a Virginia Beach courtroom while reportedly answering a traffic complaint. He later won a court battle to evict his mother from her Norfolk home, which he had purchased as a gift, saying he owed taxes and needed the money.

The court cases marked a steep downturn for a fighter who had long described boxing as a form of play and who seemed to delight as much in entertaining the crowd as in defeating his opponents.

He once pulled Roger Mayweather’s trunks down to the knees, and employed what boxing historian Bert Sugar described as “a move reminiscent of Willie Pep, slipping a punch, dipping down low, almost in a Yogi Berra-like crouch, and stepping around to tap his opponent on the back.”

Above all, Mr. Whitaker championed what he called “the most beautiful thing in the world”: hitting someone without getting hit in return.

“Most fighters don’t even know what’s happened to them,” he told Sports Illustrated in 1993. “I’ve taken something from them — their confidence, their fight plan. They can’t hit you, the fight is yours. They get self-conscious about punching. After a while they start reaching, just hoping they’re going to hit me. I don’t care who I’m fighting. I don’t care if it’s God. If I don’t want God to hit me, he’s not going to hit me.”