Oldenburg in Holstein is a town at the southwestern shore of the Baltic Sea. The nearest city is Lübeck. The town belongs to the (historical) region of Holstein, today in the state Schleswig-Holstein of Germany.

Oldenburg was the chief town of the Wagrians, one of the Slavic peoples that migrated as far west as the river Elbe in or after the 6th century (see Völkerwanderung), also known as Wends and Obotrites. They arrived about 700 AD and the Pomeranian/Kashubian (Slavic) name was Starigard or Stargard, meaning "Old Settlement", "Old Castle", "Old City/Town"; the German name Oldenburg is of Low German origin and carries the same meaning. The Obotrites were allies of Charlemagne. Emperor Otto I established the bishopric of Oldenburg under Adaldag, archbishop of Hamburg.