Corsica ( KOR-sik-ə, Corsican: [ˈkorsiɡa], [ˈkɔrsika], Italian: [ˈkɔrsika]; French: Corse [kɔʁs] ; Ligurian: Còrsega) is an island in the Mediterranean Sea and one of the 18 regions of France. It is the fourth-largest island in the Mediterranean and lies southeast of the French mainland, west of the Italian Peninsula and immediately north of the Italian island of Sardinia, the nearest land mass. A single chain of mountains makes up two-thirds of the island. As of January 2024, it had a population of 355,528.

The island is a territorial collectivity of France, and is expected to achieve "a form of autonomy" in the near future. The regional capital is Ajaccio. Although the region is divided into two administrative departments, Haute-Corse and Corse-du-Sud, their respective regional and departmental territorial collectivities were merged on 1 January 2018 to form the single territorial collectivity of Corsica. Corsican autonomy is more extensive than in other regional collectivities of France and the Corsican Assembly is permitted to exercise limited executive powers. Corsica's second-largest town is Bastia, located in the prefecture of Haute-Corse.

Corsica was ruled by the Republic of Genoa from 1284 to 1755, when it seceded to become a self-proclaimed, Italian-speaking Republic.