Alderney is the northernmost of the inhabited Channel Islands. It is part of the Bailiwick of Guernsey, a British Crown dependency. It is 3 miles (5 km) long and 1+1⁄2 miles (2.4 km) wide.

The Channel Islands are an archipelago in the English Channel, off the French coast of Normandy. They are divided into two Crown Dependencies: the Bailiwick of Jersey, which is the largest of the islands; and the Bailiwick of Guernsey, consisting of Guernsey, Alderney, Sark, Herm and some smaller islands. Historically, they are the remnants of the Duchy of Normandy. Although they are not part of the United Kingdom, the UK is responsible for the defence and international relations of the islands as it is for the other Crown Dependency, the Isle of Man, and the British Overseas Territories. The Crown Dependencies are neither members of the Commonwealth of Nations, nor part of the European Union. They have a total population of about 171,916, and the bailiwicks' capitals, Saint Helier and Saint Peter Port, have populations of 33,500 and 18,207 respectively.