Mark J. Lesko (born February 4, 1967) is an American politician and attorney who served as the acting Assistant Attorney General for the National Security Division at the United States Justice Department. Prior to that, from January 20, 2021, he was named as acting United States Attorney for the Eastern District of New York. In addition to his career as a prosecutor in the United States Department of Justice, Lesko served as town supervisor of Brookhaven, New York.