Ernest Augustus I (German: Ernst August I.) was King of Hanover from 20 June 1837 until his death. He was the fifth son and eighth child of King George III of the United Kingdom and Hanover. As a fifth son, Ernest seemed unlikely to become a monarch, but none of his four elder brothers had a legitimate son who survived infancy. The Salic Law, which barred succession to or through a female, prevailed in Hanover; therefore, when his elder brother King William IV died in 1837, Ernest succeeded him as King of Hanover. In the United Kingdom the succession to the monarchy was determined by primogeniture and his niece Victoria succeeded to the throne, thus ending the personal union between the British and Hanoverian crowns that had existed since 1714.
Ernest was born in England but was sent to Hanover in his adolescence for his education and military training. While serving with Hanoverian forces near Tournai against Revolutionary France, he received a disfiguring facial wound. In 1799, he was created Duke of Cumberland and Teviotdale. Although his marriage in 1815 to the twice-widowed Frederica of Mecklenburg-Strelitz met with the disapproval of his mother, Charlotte of Mecklenburg-Strelitz, it proved a happy one. By 1817, King George III had only one legitimate grandchild, Princess Charlotte of Wales, and when she died in childbirth, Ernest was the senior son to be both married and not estranged from his wife. This gave him some prospect of succeeding to the British throne. However, both of his unmarried older brothers quickly married, and King George's fourth son, Edward, Duke of Kent, fathered the eventual British monarch, Victoria.
Ernest was an active member of the House of Lords, where he maintained an extremely conservative voting record. There were persistent allegations (reportedly spread by his political foes) that he had murdered his valet and had fathered a son by his sister, Princess Sophia. Before Victoria succeeded to the British throne, it was rumoured that Ernest intended to murder her and take the throne himself. When King William IV died on 20 June 1837, Ernest acceded to the Hanoverian throne. Becoming Hanover's first ruler to reside in the state since George I, he had a generally successful fourteen-year reign but excited controversy when he dismissed the Göttingen Seven (including the two Brothers Grimm) from their professorial positions for agitating against his policies.