King George the 20th is the current ruling monarch of the United British Empire. Born and raised on Earth, he is a male Human. Technically, he has the power to appoint the Prime Minister and other ministers, but in practice relies on parliamentary support, especially in the House of Commons.
King George also theoretically has the power to veto bills passed by both houese of Parliament (the Commons and the Lords), but in practice he has vetoed a parliamentary bill only once. That particular bill would have banned the Ferengi from importing goods into the United Empire.