Pheasant Island (Spanish: Isla de los Faisanes, French: Île des Faisans, Basque: Konpantzia) is a river island in the Bidasoa river. The island is a condominium established by the Treaty of the Pyrenees in 1659, under joint sovereignty of Spain and France, and is administered by Irun (in Gipuzkoa, Spain) and Hendaye (in the Pyrénées-Atlantiques, France), which control the island for alternating periods of six months.