Ernst August, Crown Prince of Hanover, 3rd Duke of Cumberland and Teviotdale (Ernest Augustus William Adolphus George Frederick; 21 September 1845 – 14 November 1923), was the eldest child and only son of George V of Hanover and his wife, Marie of Saxe-Altenburg. Ernst August was deprived of the thrones of Hanover upon its annexation by Prussia in 1866 and later the Duchy of Brunswick in 1884. Although he was the senior male-line great-grandson of George III, the Duke of Cumberland was deprived of his British peerages and honours for having sided with Germany in World War I. Ernst August was the last Hanoverian prince to hold a British royal title and the Order of the Garter. His descendants are in the line of succession to the British throne.

Prince Ernest Augustus of Hanover, Duke of Brunswick-Lüneburg, Prince of the United Kingdom of Great Britain and Ireland, was born at Hanover during the reign of his paternal grandfather, Ernest Augustus I. He became the crown prince of Hanover upon his father's accession as George V in November 1851. William I of Prussia and his minister-president Otto von Bismarck deposed George V and annexed Hanover after George sided with the defeated Austria in the 1866 Austro-Prussian War. During that war, the Crown Prince saw action at the Battle of Langensalza.

After the war, the exiled Hanoverian royal family took up residence in Hietzing, near Vienna, but spent a good deal of time in Paris. George V never abandoned his claim to the Hanoverian throne and maintained the Guelphic Legion at his own expense. The former Crown Prince travelled during this early period of exile.

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