During his 13 years in Boston, Russell led the Celtics to 11 NBA championships. The last two titles he won while also serving as the NBA's first Black coach.
Russell was also a warrior for equality, a well-known civil rights activist during and long after his playing career.
The Boston Bruins posted to social media expressing their condolences.
"The Bruins mourn the passing of all-time Celtics great Bill Russell," the team said. "We extend our thoughts and condolences to his family, friends, the entire Celtics organization and all those who loved the Boston legend."
The Celtics replied to the Bruins with a green heart.
