Prince William Frederick, Duke of Gloucester and Edinburgh, KG, GCB, GCH, PC, FRS (15 January 1776 – 30 November 1834) was a great-grandson of King George II of Great Britain and the nephew and son-in-law of King George III. He was the grandson of both Frederick, Prince of Wales (George II's eldest son), and Edward Walpole. Prince William married Princess Mary, the fourth daughter of George III.
William was active in many walks of life, and on 27 April 1822 he chaired the first Annual General Meeting of London's new United University Club. Politics, however, was not among them; he entered the House of Lords rarely, and he voted on few of the great issues of his time. He did advocate the abolition of slavery, and he supported Caroline of Brunswick and Prince Augustus Frederick, Duke of Sussex, against King George IV.
The Duke of Gloucester kept more state than the King; he never permitted a gentleman to be seated in his presence (which King George did as an exceptional favour) and expected to be served coffee by the ladies of any party he attended, and that they would stand while he drank it. The general estimate of his capacity is given by his nickname, "Silly Billy"; he was also called "Slice of Gloucester" and "Cheese", a reference to Gloucester cheese.
Because of the unequal character of his parents' marriage, the Duke was excluded from the House of Hanover, being considered only a British prince. For instance, he and his sister Sophia were not listed in the genealogical listing of the electoral house of Hanover in the Königlicher Groß-Britannischer und Kurfürstlicher Braunschweig-Lüneburgscher Staats-Kalender. He was also not invited to sign the family compact of the house of Brunswick-Lüneburg in 1831, which means that he was not considered an agnate of the royal (electoral) house in Germany.
The Duke died on 30 November 1834 at Bagshot Park, and was buried in St. George's Chapel, Windsor.