The United Kingdom is made up of Great Britain, Northern Ireland, and a number of Overseas Territories. There are also several Crown Dependencies which are subject to the British Crown although not formally part of the United Kingdom. For convenience, the latter are included here.
The mainland of England, Wales, and Scotland together with their offshore islands such as the Isle of Wight and Anglesey.
The northern part of the island of Ireland, the southern part being the Republic of Ireland.
The Crown Dependencies are the Bailiwick of Guernsey, the Bailiwick of Jersey, and the Isle of Man. The two Bailwicks make up the Channel Islands, a group of islands in the English Channel off the north coast of France. The Bailiwick of Guernsey includes the islands of Alderney, Herm, Sark, and various smaller islands.
For railways in the South Orkney Islands and South Shetland Islands, see Antarctica.
There are no railways in Gibraltar, but the Spanish railway line to Algeciras was built in the late 19th Century by a British company to serve the needs of the Gibraltar garrison.
There are no railways in Montserrat. Reports of a funicular railway have sometimes arisen through confusion with the mountain location of a similarly named Benedictine abbey in Spain.
There are no railways in Akrotiri & Dhekalia, British Indian Ocean Territory, British Virgin Islands, Cayman Islands, Pitcairn Islands, or Tristan da Cunha.