The British Royal Family is the group of close relatives of the monarch of the United Kingdom. The term is also commonly applied to the same group of people as the relations of the monarch in his or her role as sovereign of any of the other Commonwealth realms, thus sometimes at variance with official national terms for the family. Members of the royal family belong to, or are married into, the House of Windsor, since 1917, when George V changed the name of the royal house from Saxe-Coburg and Gotha.

Although in the United Kingdom there is no strict legal or formal definition of who is or is not a member of the Royal Family, and different lists will include different people, those carrying the style His or Her Majesty (HM), or His or Her Royal Highness (HRH) are generally considered members, which usually results in the application of the term to: the monarch, the consort of the monarch, the widowed consorts of previous monarchs, the children of the monarch, the male-line grandchildren of the monarch, and the spouses and the widowed spouses of a monarch's son and male-line grandsons.

Members and relatives of the British Royal Family historically represented the monarch in various places throughout the British Empire, sometimes for extended periods as viceroys, or for specific ceremonies or events. Today, they often perform ceremonial and social duties throughout the United Kingdom and abroad on behalf of the UK, but, aside from the monarch, have no constitutional role in the affairs of government. This is the same for the other realms of the Commonwealth, in personal union with the United Kingdom, though the family there acts on behalf of, is funded by, and represents the sovereign of that particular state, and not Britain.