Boston Celtics Legend Tom Heinsohn Dead At 86

Hall of Famer Tom Heinsohn -- who won 10 titles for the Boston Celtics as a player and coach -- has died, the team announced Monday. He was 86.

Heinsohn is the only person to have ties to each of the Celtics' 17 championships ... going on to spend 30 years as a beloved color commentator after his coaching career.

Tom was a 6-time All-Star on the court ... winning Rookie of the Year honors in 1957. Heinsohn -- AKA "Tommy Gun" -- averaged 18.6 points in 654 games in his career.

He retired as a player in 1965 ... and the Celtics retired his #15 jersey a year later.

Heinsohn spent 9 seasons as Celtics head coach from 1969-78 -- winning titles in 1974 and 1976 -- and was named Coach of the Year in 1973.

Heinsohn was inducted into the Naismith Memorial Basketball Hall of Fame as a player in 1986 ... and was later recognized for his coaching career in 2015.

The Celtics ownership group released a statement, saying, "This is a devastating loss. Tommy was the ultimate Celtic."

"For the past 18 years, our ownership group has relied hugely on Tommy’s advice and insights and have reveled in his hundreds of stories about Red Auerbach, Bill Russell, and how the Celtics became a dynasty. He will be remembered forever.

Ex-Celtics star Isaiah Thomas mourned the loss on Tuesday ... saying, "Damn RIP Tommy Heinsohn!!!"

"'The Little guy' that’s the nickname he gave me. Will miss his voice and everything he brought to the game especially Celtics basketball."