Alderney (French: Aurigny; Auregnais: Aoeur'gny) is the most northerly of the Channel Islands. It is part of the Bailiwick of Guernsey, a British Crown dependency. It is 3 miles (4.8 km) long and 1.5 miles (2.4 km) wide. The area is 3 square miles (7.8 km²), making it the third-largest island of the Channel Islands, and the second largest in the Bailiwick. It is around 10 miles (16 km) to the west of La Hague on the Cotentin Peninsula, Normandy, in France, 20 miles (32 km) to the north-east of Guernsey and 60 miles (97 km) from the south coast of Great Britain. It is the closest of the Channel Islands to both France and the United Kingdom. It is separated from Cap de la Hague by the dangerous Race of Alderney (Le Raz Blanchard).

The island has a population of only 2,400 people and they are traditionally nicknamed vaques after the cows, or else lapins after the many rabbits seen in the island. Formally, they are known as Ridunians, from the Latin Riduna.

The only parish of Alderney is the parish of St Anne, which covers the whole island.