The House of Windsor is the reigning royal house of the United Kingdom and the other Commonwealth realms. In 1901, a line of the House of Saxe-Coburg and Gotha (itself a cadet branch of the House of Wettin) 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 because of anti-German sentiment in the United Kingdom during World War I. There have been four British monarchs of the House of Windsor since then: George V, Edward VIII, George VI, and Elizabeth II.

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

An Order in Council is a type of legislation in many countries, especially the Commonwealth realms. In the United Kingdom this legislation is formally made in the name of the monarch by and with the advice and consent of the Privy Council (Queen-in-Council), but in other countries the terminology may vary. The term should not be confused with Order of Council, which is made in the name of the Council without royal assent.