Jamaica, island country of the West Indies. It is the third largest island in the Caribbean Sea, after Cuba and Hispaniola. Jamaica is about 146 miles (235 km) long and varies from 22 to 51 miles (35 to 82 km) wide. It is situated some 100 miles (160 km) west of Haiti, 90 miles (150 km) south of Cuba, and 390 miles (630 km) northeast of the nearest point on the mainland, Cape Gracias a Dios, on the Caribbean coast of Central America. The national capital is Kingston.