Guyana, Cooperative Republic of, in full, Cooperative Republic of Guyana, republic on the northern coast of South America, formerly British Guiana, a member of the Commonwealth of Nations. It is bordered on the north by the Atlantic Ocean, on the east by Suriname, on the south by Brazil, and on the west by Brazil and Venezuela. The nation achieved freedom on May 26, 1966. Guyana has an area of 214,969 sq km (83,000 sq mi); its coastline is about 435 km (270 mi) long. The capital is Georgetown.