Thomas Kenneth Heintzelman (born November 3, 1946) is an American former professional baseball player. An infielder, he played in 90 Major League games over parts of four seasons with the St. Louis Cardinals and San Francisco Giants. He threw and batted right-handed, stood 6 feet 1 inch (1.85 m) tall and weighed 180 pounds (82 kg). Heintzelman was drafted by the Cardinals in the seventh round of the 1968 Major League Baseball Draft and made his major league debut during the 1973 season. Following the 1974 baseball season, he was traded to the Giants for Jim Willoughby.