"Red Auerbach was known best for his extraordinary success as an NBA head coach, but his leadership and passion had a profound impact away from the court," said NBA commissioner David Stern.
"Beyond his incomparable achievements, Red had come to be our basketball soul and our basketball conscience. The void left by his death will never be filled."
Auerbach, who had been in ill health for some time, "passed away suddenly" on Saturday according to a statement from the Celtics. He was 89.
The Pride of Boston
In 1950, Auerbach joined the Celtics as the franchise's third coach and also served as general manager, president and vice chairman of the board.
Auerbach guided the Celtics to their first championship as a coach-general manager in 1957 and an unprecedented eight straight titles from 1959-66, elevating them above such North American sports dynasties as baseball's New York Yankees and the National Hockey League's Montreal Canadiens for consecutive championships.
Auerbach retired as coach after the eighth straight title and appointed center Bill Russell as player-coach, but remained the team's general manager through the 1983-84 season and served as president from 1970-97 and then again starting in 2001.
From 1957-69, the Celtics won 11 championships in 13 seasons. They added five more titles in 1974, 1976, 1981, 1984 and 1986 for an NBA-high total of 16.
Former Boston great and Hall of Famer Kevin McHale recalled the tremendous impact Auerbach had on the game and on his own life.
"Red was a man who was bigger than life," McHale said.
"His impact on the game of basketball and the NBA is immeasurable. He was a huge part of my time in Boston, and for that I am forever grateful.
"The Celtics will never be quite the same without Red Auerbach."
Former Celtics forward and Golden State coach Don Nelson added, "Obviously, this is difficult news for me to accept. Red was my mentor.
"He had a tremendous impact on me as a basketball player and coach and is responsible for any success that I've had in my career. Any conversation regarding the greatest coaches in NBA history should begin with Red Auerbach.
"He was pioneer, an innovator and, most notably, an incredible winner."
Pat Riley, coach of the reigning NBA champion Miami Heat coach Pat Riley said friends and foes alike would miss Auerbach's influence.
"Today is a sad day for everybody that knew Red, that competed against him, that enjoyed watching him," Riley said.
"He was one of the great, if not the greatest coach, in the history of all of basketball."
Hall of Famer and Memphis Grizzlies president of basketball operations Jerry West also paid tribute.
"During my career, I had the misfortune of having to play against Red and his Celtics," he said.
"This truly is a passing of a legendary person in the world of basketball. Red deserved every accolade he ever earned and he will be missed deeply."