"Hitler Has Only Got One Ball", sometimes known as "The River Kwai March", is a World War II British song, the lyrics of which, sung to the tune of the World War I-era "Colonel Bogey March", impugn the masculinity of Nazi leaders by alleging they had missing, deformed, or undersized testicles. Multiple variant lyrics exist, but the most common version refers to rumours that Adolf Hitler had monorchism, and accuses Hermann Göring and Heinrich Himmler of microorchidism and Joseph Goebbels of anorchia. An alternative version suggests Hitler's missing testicle is displayed as a war trophy in the Royal Albert Hall.

The possibility that Adolf Hitler had only one testicle has been a fringe subject among historians and academics researching the Nazi leader. The rumour may be an urban myth, possibly originating from the contemporary British military song "Hitler Has Only Got One Ball".