Ramsay's death was announced by ESPN, for whom he worked as a broadcaster for many years.
"Dr. Jack Ramsay has passed," ESPN spokesman Chris LaPlaca wrote on Twitter early Monday. "A rare man. Loved and respected by all. Fascinating life well lived. An inspiration to so many."
Ramsay coached in the NBA for parts of 21 seasons before embarking on a second career as an NBA analyst. He was diagnosed with melanoma in 2004 and later battled growths and tumors that spread to his legs, lungs and brain, then later fought prostate cancer and most recently a marrow syndrome.
His affinity for fitness never wavered, though. Ramsay, who competed in at least 20 triathlons during his life, worked out regularly into his 80s, even as he battled the various forms of cancer that he was stricken with. He often spoke of his love of swimming in the Gulf of Mexico near his home in Naples, Fla., or jogging in a pool or from wall to wall in his hotel room when he was traveling on NBA assignments.
"He's probably forgotten more about the game than I know," Miami Heat coach and president Pat Riley once said of Ramsay, whom he counted as a close friend.
Ramsay also spent several years late in life caring for his wife, Jean, who was diagnosed in 2001 with Alzheimer's disease. She died in January 2010.
Ramsay had enormous popularity within the league, even until the final stages of his life. To commemorate Ramsay's 89th birthday earlier this year, Portland coach Terry Stotts wore a loud checkered jacket and open-collared shirt for a Blazers' game — a nod to how Ramsay dressed when he coached the club.
"Jack's life is a beacon which guides us all," Bill Walton, who was on Ramsay's 1977 title team in Portland, told USA Today in 2007. "He is our moral compass, our spiritual inspiration. He represents the conquest of substance over hype. He is a true saint of circumstance."
John T. Ramsay was born Feb. 21, 1925, in Philadelphia and enrolled at Saint Joseph's in 1942, eventually becoming captain of the basketball team there for his senior season. He earned a doctorate in education from the University of Pennsylvania in 1949, explaining the "Dr. Jack" moniker that most players and fans simply knew him by.
After Navy service in World War II, Ramsay graduated from St. Joseph’s in 1949. He played semipro basketball, coached in high school, then became head coach at St. Joseph’s in 1955. He coached the Hawks to 10 postseason appearances in 11 seasons, including a berth in the N.C.A.A. tournament’s Final Four in 1961, and had an overall record of 234-72.
He became the 76ers’ general manager in the 1966-67 season, when the Sixers, led by Wilt Chamberlain, won their first N.B.A. championship.
Ramsay took on the coaching as well in July 1968 when Chamberlain was traded to the Los Angeles Lakers. A year later, he became the first N.B.A. general manager to use computerized analysis in scouting college players for the draft.
"For me, it was a once-in-a-lifetime experience and one that I will cherish forever," Ramsay in an 1997 interview.