Charles Frederick, Duke of Schleswig-Holstein-Gottorp () (30 April 1700 – 18 June 1739) was a Prince of Sweden and Duke of Schleswig-Holstein-Gottorp and an important member of European royalty. His dynasty, the Dukes of Schleswig-Holstein-Gottorp, were a cadet branch of the ancient House of Oldenburg, which at that time was ruling Denmark-Norway. His mother was a sister of Charles XII of Sweden. Charles Frederick married a daughter of Peter the Great and became the father of the future Peter III of Russia. As such, he is the progenitor of the Russian imperial house of Holstein-Gottorp-Romanov and the patrilineal ancestor of all Russian emperors starting with Peter III, except for Catherine II. Early life Charles Frederick was born in Sweden, the son of Frederick IV of Schleswig-Holstein-Gottorp and his consort, Hedvig Sophia, daughter of King Charles XI of Sweden. He became reigning duke in infancy, upon his father's death in 1702 at the Battle of Kliszów, co-ruling, however under guardianship till 1717, with his father's cousin King Frederick IV of Denmark in the Duchy of Holstein, a Holy Roman imperial fief, and the Duchy of Schleswig, a Danish fief, there as a vassal to the Danish-Norwegian king. All his life he was a legitimate claimant to the throne of Sweden, as pro forma heir to Charles XII, who was his maternal uncle. Charles Frederick's parents had been offered refuge by maternal uncle, Charles XII of Sweden, during the outbreak of the Great Northern War, and they resided in Stockholm. Charles Frederick succeeded to the dukedom at the age of two, upon the death of his father in the Battle of Kliszów. His mother became his regent, and they continued to reside in Stockholm. Actual daily co-rule in the Duchies of Schleswig and Holstein was left to administrators. His mother is said to have raised him tenderly but firmly, but she died in 1708, when Charles Frederick was only eight years old. He was then placed in the care of his great-grandmother (his mother's paternal grandmother), Queen Dowager Hedwig Eleonora of Schleswig-Holstein-Gottorp, who reportedly spoiled him terribly, resulting in making him passive and indolent. His mother, and later Hedwig Eleonora, both supported and worked for his right to be considered heir of Sweden after his childless uncle. Since his guardians sided with Sweden against Denmark-Norway in the Great Northern War, Danish troops ravaged the Gottorp ducal share in the duchies during that