Sigmund Werner Paul Jähn (b. February 13, 1937) was the first German astronaut (or actually cosmonaut).
He was born in Morgenröthe-Rautenkranz, Vogtland, Germany. From 1943 to 1951 he attended school in his hometown, and after school trained as a printer. In 1955 he joined the air force of East Germany, where he became a pilot and military scientist. From 1966-1970 he studied at the Monino air force academy in the Soviet Union, and afterwards worked in the administration of the East German air force, responsible for pilot education and flight safety.
In 1976 he was selected together with his later backup Eberhard Köllner to train as the first cosmonaut in the Intercosmos program. He trained in Star City near Moscow for the next two years, and finally flew on board Soyuz 33 to the Soviet space station Salyut 6, and returned with Soyuz 29. He spent 7 days, 20 hours, and 49 minutes in space.
In 1983 he received a doctorate in physics at the "Zentralinstitut für Physik der Erde" in Potsdam, specialising in remote sensing of the earth.
Starting in 1990, (after reunification) he worked as freelance consultant for the (formerly West) German spaceflight agency DLR, and from 1993 also for the ESA to prepare for the Euromir missions. In 2002 he finally retired from this job.