Celtics legend Bill Russell, on the Mount Rushmore of Boston sports with a whopping 11 titles as a player including two championships as the first Black head coach in U.S. pro sports, died on Sunday. He was 88.

Russell, the greatest champion in basketball history with a “trademark laugh,” was also a civil rights activist who marched with Martin Luther King Jr. — and who had “an uncompromising, dignified and always constructive commitment to principle,” his family wrote in a message announcing his passing.

“Bill Russell, the most prolific winner in American sports history, passed away peacefully today at age 88, with his wife, Jeannine, by his side,” his family wrote.

His iconic accolades include a record 11 NBA championships and five MVP awards. He won two of the 11 titles as a player-coach. One of the greatest defensive players of all time, he had a unique ability to block shots while keeping the ball inbounds to start a fast break.

In addition to all his unprecedented winning on the court, Russell is remembered for his decades of social justice activism.

“… Bill’s understanding of the struggle is what illuminated his life,” the family message stated.

“From boycotting a 1961 exhibition game to unmask too-long-tolerated discrimination, to leading Mississippi’s first integrated basketball camp in the combustible wake of Medgar Evans’ assassination, to decades of activism ultimately recognized by his receipt of the Presidential Medal of Freedom in 2010,” the message continued. “Bill called out injustice with an unforgiving candor that he intended would disrupt the status quo, and with a powerful example that, though never his humble intention, will forever inspire teamwork, selflessness, and thoughtful change.”

Russell would talk about playing for the Celtics institution but not playing for Boston and the fans, who blasted him with racist taunts. His Reading home was broken into and vandalized.

“Police cars followed me often,” Russell wrote for SLAM Magazine two years ago. “I looked into buying a different house in a different neighborhood, but people in that neighborhood started a petition to persuade the seller not to sell to me.”

In Boston, there’s a statue of Russell on City Hall Plaza.

NBA Commissioner Adam Silver in a statement called Russell “the greatest champion in all of team sports.”

“Bill stood for something much bigger than sports: the values of equality, respect and inclusion that he stamped into the DNA of our league,” Silver said. “At the height of his athletic career, Bill advocated vigorously for civil rights and social justice, a legacy he passed down to generations of NBA players who followed in his footsteps. Through the taunts, threats and unthinkable adversity, Bill rose above it all and remained true to his belief that everyone deserves to be treated with dignity.”

Former President Barack Obama tweeted, “Today, we lost a giant. As tall as Bill Russell stood, his legacy rises far higher — both as a player and as a person.”

WASHINGTON, DC - FEBRUARY 15: U.S. President Barack Obama (L) presents Basetball Hall of Fame member and human rights advocate Bill Russell the 2010 Medal of Freedom in the East Room of the White House February 15, 2011 in Washington, DC. Obama presented the medal to twelve pioneers in sports, labor, politics and arts. (Photo by Chip Somodevilla/Getty Images)
WASHINGTON, DC – FEBRUARY 15: U.S. President Barack Obama (L) presents Basetball Hall of Fame member and human rights advocate Bill Russell the 2010 Medal of Freedom in the East Room of the White House February 15, 2011 in Washington, DC. Obama presented the medal to twelve pioneers in sports, labor, politics and arts. (Photo by Chip Somodevilla/Getty Images) 
(073022 Boston, MA):The Boston Red Sox honored Bill Russell before the game at Fenway Park on Saturday,July 30, 2022 in Boston, MA. (Staff Photo By Nancy Lane/MediaNews Group/Boston Herald)
(073022 Boston, MA):The Boston Red Sox honored Bill Russell before the game at Fenway Park on Saturday,July 30, 2022 in Boston, MA. (Staff Photo By Nancy Lane/MediaNews Group/Boston Herald) 
FILE - Boston Celtics legendary center Bill Russell has a light moment while answering questions from members of the media after a Celtics team practice in Waltham, Mass., Oct. 11, 1999. The NBA great Bill Russell has died at age 88. His family said on social media that Russell died on Sunday, July 31, 2022. Russell anchored a Boston Celtics dynasty that won 11 titles in 13 years. (AP Photo/Angela Rowlings)
FILE – Boston Celtics legendary center Bill Russell has a light moment while answering questions from members of the media after a Celtics team practice in Waltham, Mass., Oct. 11, 1999. The NBA great Bill Russell has died at age 88. His family said on social media that Russell died on Sunday, July 31, 2022. Russell anchored a Boston Celtics dynasty that won 11 titles in 13 years. (AP Photo/Angela Rowlings) 
'WAY OVERDUE': While fans cheer on the Celtics during the Finals, Kilbert Pierce, a Brockton ex-boxer, is working with the Hub to find a way to honor legend Bill Russell.
‘WAY OVERDUE’: While fans cheer on the Celtics during the Finals, Kilbert Pierce, a Brockton ex-boxer, is working with the Hub to find a way to honor legend Bill Russell.