The largest lake in the world by surface area is the Caspian Sea. Despite its name, the Caspian Sea is classified as a lake because it is an enclosed body of water, lacking an outlet to the ocean. It covers approximately 371,000 square kilometers (143,000 square miles) and is bordered by five countries: Russia, Kazakhstan, Turkmenistan, Iran, and Azerbaijan. The Caspian Sea is notable for its unique biodiversity, including species such as the beluga sturgeon and various endemic fish. Its economic significance is substantial, with rich oil and gas reserves, making it a strategic region for energy resources.