Ludwig Ernest Frank Langer (January 22, 1893 – July 5, 1984) was an American competition swimmer who competed in freestyle events. He was one of six Hawaii-based swimmers who competed at the 1920 Summer Olympics and collectively won seven medals. Langer won a silver medal in the 400-meter freestyle, but failed to reach the final of the 1,500-meter freestyle.
Domestically Langer won the 440-yard, 880-yard and one-mile freestyle events at the 1915 and 1916 Amateur Athletic Union (AAU) championships. He won his seventh AAU title in 1921, beating Johnny Weissmuller in the 440-yard freestyle. By 1916 he held world records over 440-yard, 880-yard and one-mile distances, but could not compete in the Olympics due to World War I.
In 1988 he was posthumously inducted into the International Swimming Hall of Fame.