Which tiny river island is a condominium alternating between France and Spain?

Pheasant Island is the tiny river island that forms a condominium between France and Spain.

The uninhabited island lies in the Bidasoa River, between the French town of Hendaye and the Spanish city of Irun. It is jointly sovereign territory rather than a normal divided island: France and Spain share ownership, while practical administration alternates between them.

Spain administers Pheasant Island from 1 February through 31 July, and France administers it from 1 August through 31 January. The arrangement is linked to the Treaty of the Pyrenees, signed on the island in 1659 to end the long conflict between the two kingdoms. The island covers only about 0.682 hectares and is often described as the world’s smallest condominium.

A common misconception is that the island permanently changes nationality or is split into French and Spanish halves. Its sovereignty is shared continuously; what changes every six months is the government exercising administrative authority. Because it is uninhabited and access is restricted, it is primarily a historical and geographic curiosity rather than a conventional settlement.