The sports world mourns as NBA great Bill Russell, who won 11 championships during a Hall of Fame career spent entirely with the Boston Celtics, died on Sunday, July 31.

Here are personalities who reacted to his death:

US President Joe Biden

“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.”

Former US President Barack Obama

“Today, we lost a giant. 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. On the court, he was the greatest champion in basketball history. Off of it, he was a civil rights trailblazer – marching with Dr. King and standing with Muhammad Ali.”

Bernice King, daughter of Martin Luther King Jr.

“What a trailblazer who transcended sports in influencing our national and global landscape.”

“A champion in many ways that matter.”

“Thank you and rest in power, Sir #BillRussell.”

Bulls legend Michael Jordan

“Bill Russell was a pioneer – as a player, as a champion, as the NBA’s first Black head coach, and as an activist.”

“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.”

Lakers icon Magic Johnson

“I’m heartbroken to hear about the passing of the greatest winner the game of basketball has ever seen, a legend, hall of famer, mentor, and my friend for over 30 years, Bill Russell.”

“Bill Russell was my idol. I looked up to him on the court and off. His success on the court was undeniable … winning 11 NBA championships. Off the court, Bill Russell paved the way for guys like me.”

“He was one of the first athletes on the front line fighting for social justice, equity, equality, and civil rights. That’s why I admired and loved him so much. Over the course of our friendship, he always reminded me about making things better in the Black community.”

Tennis great Billie Jean King

“Bill Russell was a once-in-a-generation activist athlete who made all around him better. He had a career of firsts and led the way for many. I admired him my entire life and he had a huge influence on my career. He was the ultimate leader, ultimate team player, and ultimate champion.”

NBA commissioner Adam Silver

“I often called him basketball’s Babe Ruth for how he transcended time. Bill was the ultimate winner and consummate teammate, and his influence on the NBA will be felt forever.”

NBPA executive director Tamika Tremaglio

“At a time when it was far more difficult and dangerous to do so, Bill used his voice openly and fearlessly to serve as a fierce advocate for equality, civil rights, and social justice.”

“His actions laid the foundation not just for NBA players, but for professional athletes from all sports and others, to stand up and call for change in the face of racial injustice and inequality.”

“Bill was also a founding father of our Players Association, one of the legendary 1964 All-Stars who barricaded himself in the locker room insisting that management recognize our union.”

Former NFL head coach Tony Dungy

“He was one of my heroes – not only a sports legend but a tremendous leader. Russell changed the landscape of sports in America by fighting for equality for everyone – on and off the field. Many of us tried to follow in his footsteps.”

Comedian Jon Stewart

“Bill Russell was one of the kindest, most thoughtful people I’ve ever met. Once called out of the blue because he thought I looked sad on TV … best pep talk of my life. RIP.”

Pistons icon Isiah Thomas

“Rest in peace Bill Russell you were everything we all aspired to be, your winning spirit will live forever my friend. Thank you for your words of wisdom.”

Boston Celtics

“Bill Russell’s DNA is woven through every element of the Celtics organization, from the relentless pursuit of excellence, to the celebration of team rewards over individual glory, to a commitment to social justice and civil rights off the court.”

Boston Mayor Michelle Wu

“Bill Russell gave so much to the city of Boston – as the greatest sports champion of all time and a role model fighting for justice, equality, and labor rights.”

“We owe him a debt of gratitude and we will miss him.”

USA Basketball

“USA Basketball mourns the loss of basketball titan, humanitarian, and 1956 Olympic gold medalist Bill Russell.” – Rappler.com