William IV (William Henry) was King of the United Kingdom of Great Britain and Ireland and King of Hanover from 26 June 1830 until his death. The third son of George III and younger brother and successor to George IV, he was the last king and penultimate monarch of Britain's House of Hanover.
The royal style of King William IV was "By the Grace of God, of the United Kingdom of Great Britain and Ireland King, Defender of the Faith, King of Hanover, Duke of Brunswick-Luneburg".
The title King of Gibraltar continues to be used by Spanish monarchs even though the territory was ceded to the Crown of Great Britain in perpetuity under the terms of the Treaty of Utrecht of 1713. The continued use of the title thus emphasizes a Spanish viewpoint that the British monarch merely has possession of Gibraltar, rather than sovereignty over it. The United Kingdom, by contrast, takes the position that the treaty transferred sovereignty as well as possession. It was customary for titles and arms of conquered territories to be omitted from British regnal claims. The title and arms were thus never claimed by the British monarchy.