Sigmund Werner Paul Jähn (born 13 February 1937) is a German pilot who became the first German to fly in space as part of the Soviet Union's Interkosmos program.

During and after the flight, he and the socialist authorities of the GDR pronounced him "the first German cosmonaut", which was remarkable, as in those days the East German state normally stressed that their people were "GDR citizens", to distinguish themselves from West Germany.