Jack A. Gillespie (born October 1, 1947) is a retired professional basketball forward who played one season in the American Basketball Association (ABA) as a member of the New York Nets during the 1969–70 season.
He graduated from Great Falls High School, Great Falls, Montana where he led the team to a Montana High School Basketball Championship in 1965. He attended Montana State University where he finished his college career as the school's all-time leader in rebounds (1,011) and points (1,543) along with two Big Sky Conference Player of the Year awards. Gellespie went on to be inducted into the Montana State Bobcats' Hall of Fame.
He was selected in the 12th (166th pick overall) round of the 1969 NBA Draft by the Los Angeles Lakers, but never signed.