Corsica is a French island in the Mediterranean Sea. It is located west of Italy, southeast of the French mainland, and north of the Italian island of Sardinia. Mountains comprise two-thirds of the island, forming a single chain. Before French domination, Corsica was under the ownership of the Republic of Genoa. Corsica is one of the 27 régions of France, although it is designated as a territorial collectivity (collectivité territoriale) by law.