Louis Laddie Koupal (December 19, 1898 – December 8, 1961) born in Tabor, South Dakota, was a pitcher for the Pittsburgh Pirates (1925–26), Brooklyn Robins (1928–29), Philadelphia Phillies (1929–30) and St. Louis Browns (1937). Koupal was of Czech descent. As a rookie in 1925, he appeared in six games, all in relief, for the Pirates, who would go on to win the World Series, though Koupal did not pitch in the postseason. Koupal died in San Gabriel, California at the age of 62.