Bill Russell redefined how basketball is played, and then he changed the way sports are viewed in a racially divided country.

The most prolific winner in NBA history, Russell marched with Martin Luther King Jr., stood with Muhammad Ali and received the Presidential Medal of Freedom from President Barack Obama. The centerpiece of the Boston Celtics dynasty that won 11 championships in 13 years, Russell earned his last two NBA titles as a player-coach — the first Black coach in any major U.S. sport.

Russell died Sunday at the age of 88, with his wife, Jeannine, at his side, his family said in a statement posted on social media. No cause of death was immediately available; Russell, who had been living in the Seattle area, was not well enough to present the NBA Finals MVP trophy in June due to a long illness.

“We hope each of us can find a new way to act or speak up with Bill’s uncompromising, dignified and always constructive commitment to principle,” the family said. “That would be one last, and lasting, win for our beloved #6.”

A Hall of Famer, five-time Most Valuable Player and 12-time All-Star, Russell in 1980 was voted the greatest player in the NBA history by basketball writers. He remains the sport’s most decorated champion — he also won two college titles and an Olympic gold medal — and an archetype of selflessness who won with defense and rebounding while others racked up gaudy scoring totals.

Often, that meant Wilt Chamberlain, the only worthy rival of Russell’s era and his prime competition for rebounds, MVP trophies and barroom arguments about who was better. Chamberlain, who died in 1999 at 63, had twice as many points, four MVP trophies of his own and is the only person in league history to grab more rebounds than Russell — 23,924 to 21,620.

But Russell dominated in the only stat he cared about: 11 championships to two.

“Bill Russell was the greatest champion in all of team sports,” NBA Commissioner Adam Silver said. More importantly, he added: “Bill stood for something much bigger than sports: the values of equality, respect and inclusion that he stamped into the DNA of our league.”

In a statement released by the White House, President Joe Biden praised Russell for his lifelong work in civil right as well as in sports, and called him “a towering champion for freedom, equality, and justice.”

“Bill Russell is one of the greatest athletes in our history – an all-time champion of champions, and a good man and great American who did everything he could to deliver the promise of America for all Americans,” Biden said.

Reaction poured in Sunday, from Obama to Michael Jordan, from Magic Johnson to Boston’s Mayor, Michelle Wu.

“Today, we lost a giant,” Obama said. “As tall as Bill Russell stood, his legacy rises far higher — both as a player and as a person. Perhaps more than anyone else, Bill knew what it took to win and what it took to lead.”

A Louisiana native, Russell also left a lasting mark as a Black athlete in a city — and country — where race is often a flash point. He was at the March on Washington in 1963, when King gave his “I Have a Dream” speech, and he backed Ali when the boxer was pilloried for refusing induction into the military draft.

In 2011, Obama awarded Russell the Medal of Freedom alongside Congressman John Lewis, billionaire investor Warren Buffett, then-German Chancellor Angela Merkel and baseball great Stan Musial.

“To be the greatest champion in your sport, to revolutionize the way the game is played, and to be a societal leader all at once seems unthinkable,” the Celtics said on Sunday. “But that is who Bill Russell was.”

Russell said that when he was growing up in the segregated South and later California his parents instilled in him the calm confidence that allowed him to brush off racist taunts.

“Years later, people asked me what I had to go through,” Russell said in 2008. “Unfortunately, or fortunately, I’ve never been through anything. From my first moment of being alive was the notion that my mother and father loved me.” It was Russell’s mother who would tell him to disregard comments from those who might see him playing in the yard.

“Whatever they say, good or bad, they don’t know you,” he recalled her saying. “They’re wrestling with their own demons.”

But it was Jackie Robinson who gave Russell a road map for dealing with racism in his sport: “Jackie was a hero to us. He always conducted himself as a man. He showed me the way to be a man in professional sports.”

The feeling was mutual, Russell learned, when Robinson’s widow, Rachel, called and asked him to be a pallbearer at her husband’s funeral in 1972.

“She hung the phone up and I asked myself, ‘How do you get to be a hero to Jackie Robinson?’” Russell said. “I was so flattered.”

William Felton Russell was born on Feb. 12, 1934, in Monroe, Louisiana. He was a child when his family moved to the West Coast, and he went to high school in Oakland, California, and then the University of San Francisco. He led the Dons to NCAA championships in 1955 and 1956 and won a gold medal in 1956 at the Melbourne Olympics in Australia.

Celtics coach and general manager Red Auerbach so coveted Russell that he worked out a trade with the St. Louis Hawks for the second pick in the draft. He promised the Rochester Royals, who owned the No. 1 pick, a lucrative visit by the Ice Capades, which were also run by Celtics owner Walter Brown.

Still, Russell arrived in Boston to complaints that he wasn’t that good. “People said it was a wasted draft choice, wasted money,” he recalled. “They said, ‘He’s no good. All he can do is block shots and rebound.’ And Red said, ‘That’s enough.’”

The Celtics also picked up Tommy Heinsohn and K.C. Jones, Russell’s college teammate, in the same draft. Although Russell joined the team late because he was leading the U.S. to the Olympic gold, Boston finished the regular season with the league’s best record.

The Celtics won the NBA championship — their first of 17 — in a double-overtime seventh game against Bob Pettit’s St. Louis Hawks. Russell won his first MVP award the next season, but the Hawks won the title in a finals rematch. The Celtics won it all again in 1959, starting an unprecedented string of eight consecutive NBA crowns.

A 6-foot-10 center, Russell never averaged more than 18.9 points during his 13 seasons, each year producing more rebounds than points. For 10 seasons he averaged more than 20 rebounds. He once had 51 rebounds in a game; Chamberlain holds the record with 55.

Auerbach retired after winning the 1966 title, and Russell became the player-coach — the first Black head coach in NBA history, and almost a decade before Frank Robinson took over Cleveland in baseball’s American League. Boston’s title streak ended with a loss to Chamberlain and the Philadelphia 76ers in the Eastern Division finals.

Russell led the Celtics back to titles in 1968 and ’69, each time winning seven-game playoff series against Chamberlain. Russell retired after the ’69 finals, returning for a relatively successful — but unfulfilling — four-year stint as coach and GM of the Seattle SuperSonics and a less fruitful half season as coach of the Sacramento Kings.

Russell’s No. 6 jersey was retired by the Celtics in 1972. He earned spots on the NBA’s 25th anniversary all-time team in 1970, 35th anniversary team in 1980 and 75th anniversary team. In 1996, he was hailed as one of the NBA’s 50 greatest players.

In 2009, the MVP trophy of the NBA Finals was named in his honor. (Russell never won the honor, because it was awarded for the first time in 1969.) He presented his namesake trophy for many years, the last in 2019 to Kawhi Leonard; Russell was not there in 2020 because of the NBA bubble nor in 2021 due to COVID-19 concerns.

In 2013, a statue was unveiled on Boston’s City Hall Plaza of Russell surrounded by blocks of granite with quotes on leadership and character. Russell was inducted into the Basketball Hall of Fame in 1975 but did not attend the ceremony, saying he should not have been the first African American elected. (Chuck Cooper, the NBA’s first Black player, was his choice.)

In 2019, Russell accepted his Hall of Fame ring in a private gathering.

“I felt others before me should have had that honor,” he tweeted. “Good to see progress.”

But to Jordan, Russell stood alone.

“Bill Russell was a pioneer — as a player, as a champion, as the NBA’s first Black head coach and as an activist,” the former Chicago Bulls star and current Charlotte Hornets majority owner said. “He paved the way and set an example for every Black player who came into the league after him, including me. The world has lost a legend.”

Russell’s family said arrangements for the memorial service will be announced in the coming days.