Rex Gildo (July 2, 1936 – October 26, 1999) was a German singer of Schlager ballads who reached the height of his popularity in the 1960s and 1970s, selling over 25 million records and starring in film and television roles.

Gildo was born Ludwig Franz Hirtreiter in Straubing, Bavaria; in the mid-fifties he adopted the stage name Alexander Gildo, later shortening it to Rex Gildo. For years he claimed that he had been a member of the Regensburger Domspatzen choir before attending acting school, while a documentary on German TV in 2009 revealed that in fact he had worked in a decorating apprenticeship before he met Fred Miekley, who would become his manager and longtime companion and presumably paid for Gildo's acting, dancing and singing lessons. Gildo's first performance was with the Munich Kammerspiele theatre group in 1956, but he quickly moved into television and film, as well as performing as a singer, most famously duetting with Danish singer Gitte Haenning as "Gitte & Rex".