Mark Heimann is an American chess grandmaster and machine learning researcher. He started playing at five, when his father bought a chess set for him and his twin brother, and went on to win national grade-level titles and both the Pennsylvania and Ohio state championships. By February 2008 he was the top-ranked under-14 player in the United States.

He starred for Washington University in St. Louis at the Pan-American Intercollegiate Championships, helping the team to a Division II title, and completed his Grandmaster title in 2025 - proof that a research career and a GM title can be built side by side.