Ernest Augustus was duke of Brunswick-Lüneburg and ruled over the Principality of Calenberg subdivision of the duchy.
Background
Ernest Augustus was born at Herzberg am Harz, the son of George, Duke of Brunswick-Lüneburg and Anne Eleonore of Hesse-Darmstadt (Ernest Augustus was descended from the Albertinian line of the Habsburg family and also the House of Hohenzollern).
Career
He was appointed prince-elector, but died before the appointment became effective. He was also Administrator of the Prince-Bishopric of Osnabrück. As the fourth son, he had little chance of succeeding his father as ruler, and so, in 1662, his relatives appointed him administrator of Osnabrück.
According to the Peace of Westphalia, every second incumbent of the Osnabrück see was to be appointed by the dukes of Brunswick-Lüneburg.
In 1683, against the protestations of his five younger sons, Ernest Augustus instituted primogeniture, so that his territory would not be further subdivided after his death, and also as a pre-condition for obtaining the coveted electorship. He participated in the Great Turkish War on the side of Leopold I, Holy Roman Emperor.
In 1692 he was appointed prince-elector by the Emperor. However, the electorship did not come into effect until 1708.