Marquette announced Thompson died on Wednesday at his Milwaukee home due to complications from diabetes.
Thompson scored 1,773 points for Marquette and owned the school's career scoring record for 40 years. Thompson now ranks fourth on Marquette's career scoring list, behind Markus Howard, Jerel McNeal and Lazar Hayward.
He averaged 20.2 points during his Marquette career, when the team posted a combined record of 68-20 during Thompson's three seasons.
"George is really the one who got everything started at Marquette," current coach Shaka Smart said in a statement. "There aren't words that can express how important he was to this program. The reverence with which former players and fans alike speak of George is second to none. We've lost a true legend."
Thompson played five seasons in the ABA with the Pittsburgh Pipers/Condors (1969-72) and Memphis Tams (1972-74) before spending the 1974-75 season with the Milwaukee Bucks.
He stayed in the Milwaukee area after his playing career and was a longtime analyst on Marquette radio broadcasts.
"George's name is synonymous with Marquette basketball," Marquette athletic director Bill Scholl said in a statement. "He was part of the foundation our program was built on and his career speaks for itself. He had a lasting impact on our university, and we mourn the loss with our entire Marquette family."