Corsica 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 …Corsica 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.