Dennis Kay Aust (born November 25, 1940) is an American former Major League Baseball pitcher. Aust played in 15 games, all as a reliever, for the St. Louis Cardinals in 1965 and 1966. He batted and threw right-handed, stood 5 feet 11 inches (1.80 m) tall and weighed 180 pounds (82 kg). In his 15 MLB relief appearances, Aust posted a 0–1 won–lost record and a 5.82 earned run average, with two saves. In 17 career innings pitched, he surrendered 18 hits and eight bases on balls with 14 strikeouts. Aust's professional baseball career concluded in 1968.