Prince William, Duke of Gloucester and Edinburgh, KG PC FRS (William Henry; 25 November 1743 – 25 August 1805), was a grandson of King George II and a younger brother of King George III of the United Kingdom.

Prince William Henry was born at Leicester House, London. His parents were Frederick, Prince of Wales, eldest son of George II and Caroline of Ansbach, and Princess Augusta of Saxe-Gotha, then Princess of Wales. He was christened at Leicester House eleven days later. His godparents were his paternal uncle by marriage, the Prince of Orange (for whom someone stood proxy); his paternal uncle, the Duke of Cumberland; and his paternal aunt, Princess Amelia. As a grandchild of the sovereign, he was styled His Royal Highness Prince William at birth. He was fourth in the line of succession at birth.

His father died in 1751, leaving the Prince's elder brother, Prince George, heir-apparent to the throne. He succeeded as George III on 25 October 1760, and created William Duke of Gloucester and Edinburgh and Earl of Connaught on 19 November 1764. He had been made a Knight of the Garter on 27 May 1762, and invested on 22 September of that year. In 1764 he began to court Maria Walpole, the Dowager Countess of Waldegrave, an illegitimate granddaughter of Sir Robert Walpole.