 Fischer was born in Gerabronn in Baden-Württemberg, the third child of a butcher, whose family had lived in Budakeszi, Hungary, for several generations.Fischer's family had to leave Hungary in 1946 after it was occupied by the Soviet Union, and ethnic Germans were persecuted and expelled by the authorities.His nickname "Joschka" is derived from the Hungarian "Jóska", diminutive of Joseph (Hungarian "József").