The House of Windsor is the reigning house of the United Kingdom and the other Commonwealth realms. The house's name was inspired by the historic Windsor Castle estate. The house was founded on 17 July 1917, when King George V changed the name of the royal house from the German Saxe-Coburg and Gotha to the English Windsor due to anti-German sentiment during the First World War. There have been five British monarchs of the House of Windsor: George V, Edward VIII, George VI, Elizabeth II, and Charles III. The children and male-line descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh, also genealogically belong to the House of Oldenburg^[1] since Philip was by birth a member of the Glücksburg branch of that house.^[2]

The monarch is head of state of fifteen sovereign states. These are the United Kingdom, Antigua and Barbuda, Australia, The Bahamas, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, and Tuvalu. As well as these separate monarchies, there are also three Crown Dependencies, fourteen British Overseas Territories, two associated states of New Zealand, and one territory.

In 1701, succession to the throne was given to Sophia of Hanover, who was born into the House of Wittelsbach, married into the House of Hanover, and was a granddaughter of James VI and I of the House of Stuart. Succession was passed to her son who became George I in 1714, marking the start of a long ruling period by the Hanoverian royal house. Eventually in 1901, a line of the House of Saxe-Coburg and Gotha succeeded the House of Hanover to the British monarchy with the accession of King Edward VII, son of Queen Victoria and Prince Albert of Saxe-Coburg and Gotha. In 1917, the name of the British royal house was changed from the German Saxe-Coburg and Gotha to the English Windsor, taking its name from the royal residence in Berkshire.^[3]

King Edward VII and, in turn, his son, George V, were members of the Saxe-Coburg and Gotha branch of the House of Wettin by virtue of their descent from Albert, Prince Consort, husband of Queen Victoria, the last British monarch from the House of Hanover. High anti-German sentiment amongst the people of the British Empire during the First World War^[4] reached a peak in March 1917, when the Gotha G.IV, a heavy aircraft capable of crossing the English Channel, began bombing London directly and became a household name. In the same year, on 15 March, King George's first cousin Emperor Nicholas II of Russia was forced to abdicate, which raised the spectre of the eventual abolition of all the monarchies in Europe. The king and his family were finally persuaded to abandon all titles held under the German Crown and to change German titles and house names to anglicised versions. Hence, on 17 July 1917, a royal proclamation issued by George V declared:

Now, therefore, We, out of Our Royal Will and Authority, do hereby declare and announce that as from the date of this Our Royal Proclamation Our House and Family shall be styled and known as the House and Family of Windsor, and that all the descendants in the male line of Our said Grandmother Queen Victoria who are subjects of these Realms, other than female descendants who may marry or may have married, shall bear the said Name of Windsor....^[5]

The name had a long association with monarchy in Britain, through the town of Windsor, Berkshire, and Windsor Castle. It was suggested by Arthur Bigge, 1st Baron Stamfordham.^[6] Upon hearing that his cousin had changed the name of the British royal house to Windsor and in reference to Shakespeare's The Merry Wives of Windsor, German Emperor Wilhelm II remarked jokingly that he planned to see "The Merry Wives of Saxe-Coburg-Gotha".^[7]

George V also restricted the use of British princely titles to his nearest relations,^[8] and in 1919, he stripped three of his German relations of their British titles and styles under the Titles Deprivation Act 1917.^[9]

The children and male-line descendants of Queen Elizabeth II and Prince Philip also genealogically belong to the House of Oldenburg^[1] since Philip was by birth a member of the Glücksburg branch of that house.^[2]

The 1917 proclamation stated that the name of the Royal House and all British descendants of Victoria and Albert in the male line were to bear the name of Windsor, except for women who married into other families.

At the creation of the House of Windsor, its head reigned over the British Empire. Following the end of the First World War, however, shifts took place that saw the emergence of the Dominions of the British Commonwealth as independent states. The shift was recognised in the Balfour Declaration of 1926,^[14][15] the Royal and Parliamentary Titles Act 1927,^[16][17] and the Statute of Westminster 1931.^[18][19] The Windsors became recognised as the royal family of multiple independent countries, a number that shifted over the decades, as some Dominions became republics and Crown colonies became realms, republics, or monarchies under a different sovereign.^[20] Since 1949, three monarchs of the House of Windsor, George VI, Elizabeth II and Charles III, have also been Head of the Commonwealth of Nations, comprising most parts of the former British Empire and some states that were never part of it.^[21][22][23]

• List of current British princes and princesses
• British royal family
• Monarchy of Canada § Royal family and house
• British prince
• British princess
• Descendants of George V
• Succession to the British throne