Christian August of Holstein-Gottorp, Prince of Eutin

Prince Christian August of Holstein-Gottorp (11 January 1673 – 24 April 1726) was Duke of Slesvig-Holstein, prince regent of Eutin, prince-bishop of Lübeck and regent of the duchy of Holstein-Gottorp.

He was a younger son of Christian Albert, Duke of Holstein-Gottorp and Princess Frederica Amalia of Denmark, daughter of King Frederick III of Denmark and Norway. Therefore, it was his eldest brother, Frederick IV, Duke of Holstein-Gottorp, who naturally succeeded their father as ruler of the small principality, with Christian August given the tiny fiefdom of Eutin. Additionally, his family managed to have him elected as the Lutheran bishop of Lübeck, which at the time entailed a sovereign princely position in the Holy Roman Empire.

When his eldest brother died in 1702, leaving only an underage son (Charles Frederick, Duke of Holstein-Gottorp) as his heir, and his sister-in-law, the regent Hedvig Sophia of Sweden died a few years later, Christian August was installed as administrator (under the superiority of his sister-in-law) and then (after his sister-in-law's death in 1708) full regent of their principality of Holstein-Gottorp, which was severely ravaged by the violence of Great Northern War.

Prince Christian August married Albertina Frederica of Baden-Durlach (3 July 1682-26 December 1755), on 2 September 1704, with whom he had ten children.

• Hedwig Sophie Auguste of Holstein-Gottorp (9 October 1705-4 October 1764), Abbess of Herford, 1750–1764
• Charles Augustus of Holstein-Gottorp (26 November 1706-31 May 1727)
• Frederica Amalia of Holstein-Gottorp (12 January 1708-19 January 1782), a nun at Quedlinburg
• Anne of Holstein-Gottorp (3 February 1709-2 February 1758); m. William, Duke of Saxe-Gotha
• Adolf Frederick of Eutin (14 May 1710-12 April 1771), became crown prince of Sweden in 1743, and then ascended the throne of King of Sweden in 1751.
• Frederick August of Eutin (20 September 1711-6 July 1785), received the position of bishop of Lübeck, after Adolf Frederick (who held it until going to Sweden), as well as the fiefdom of Eutin. In 1773, Frederick August received Oldenburg and Delmenhorst from their young cousin (and future Tsar of Russia), Paul, Duke of Holstein-Gottorp, thus adding the state of Oldenburg which would become a Grand Duchy much later.
• Joanna Elisabeth (24 October 1712-30 May 1760), became a princess of Anhalt through marriage with Christian August, Prince of Anhalt-Zerbst, and mothered Catherine the Great, Empress regnant of Russia.
• William Christian of Holstein-Gottorp (20 September 1716-26 June 1719)
• Frederick Conrad of Holstein-Gottorp (12 March 1718-1719)
• George Louis of Holstein-Gottorp (16 March 1719-7 September 1763) father of Peter I, Grand Duke of Oldenburg

Christian August was succeeded by his sons Charles Augustus, who died before factually taking office, and then Adolf Frederick.