Friedrich August, Duke of Holstein-Oldenburg^{[citation needed]} (20 September 1711 in Gottorp, Schleswig^{[citation needed]} – 6 July 1785 in Oldenburg^{[citation needed]}) was the son of Christian August, regent of Holstein-Gottorp and his wife Margravine Albertine Friederike of Baden-Durlach.^{[citation needed]}

Frederick Augustus married on 21 November 1752 to Princess Ulrike Friederike Wilhelmine of Hesse-Kassel; the couple had three children:^{[citation needed]}

• Peter Friedrich Wilhelm, Duke of Oldenburg (3 January 1754 – 2 July 1823)^{[citation needed]}
• Luise of Holstein-Gottorp-Oldenburg (2 October 1756 – 31 July 1759),^{[citation needed]} died in infancy
• Hedwig Sophie Charlotte (22 March 1759 – 20 June 1818), Queen of Sweden and Norway as wife of Charles XIII of Sweden.^{[citation needed]}

Empress Catherine the Great of Russia, on behalf of her son Paul of Russia, last of the Dukes of Holstein-Gottorp, ceded the lands of that duchy to Denmark. In exchange, Denmark ceded the Duchy of Oldenburg to the Prince Bishops of Lübeck, a cadet branch of the Dukes of Gottorp. Thus, Friederich August of Holstein-Gottorp, Prince Bishop of Lübeck, became Duke of Oldenburg.^{[citation needed]}

His son and heir apparent, Peter Friedrich Wilhelm, succeeded him as Wilhelm I, Duke of Oldenburg.

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• Rulers of Oldenburg