Reid was 68 years old ... and had been battling an illness, according to the Houston Chronicle.

The Rockets announced the sad news on Tuesday, writing, "The Fertitta Family and the Houston Rockets are deeply saddened by the passing of former player, Robert Reid, whose contributions were instrumental in guiding the Houston Rockets to their first two NBA Finals appearances in 1980-81 and 1985-86."

Reid, a 6'8" guard/forward who was a second-round draft pick in 1977, averaged 11.4 points, 4.5 rebounds, 2.7 assists, and 1.1 blocks a game during his NBA career -- 10 seasons of which were spent in Houston, just a few hours from where he grew up in San Antonio, TX.

He also played for the Charlotte Hornets, Portland Trail Blazers, and Philadelphia 76ers.

Reid, who was teammates with the legendary Moses Malone, scored 10,448 points in 919 NBA games.

Current Rockets owner Tilman Fertitta also reacted to news of Reid's death, saying ... "It is with great sorrow that my family and I received the news of the passing of Rockets legend, Robert Reid. I have had the privilege of knowing Robert for over 40 years, and his presence always brought joy and positivity to any room he entered."

Reid was 68.