Melanesia is a subregion of Oceania extending from New Guinea island in the southwestern Pacific Ocean to the Arafura Sea, and eastward to Tonga. The region includes the four independent countries of Vanuatu, Solomon Islands, Fiji, and Papua New Guinea, as well as the French special collectivity of New Caledonia, and the Indonesian region of Western New Guinea. Most of the region is in the Southern Hemisphere, with a few small northwestern islands of Western New Guinea in the Northern Hemisphere.
A distinction is often made between the island of New Guinea and what is known as Island Melanesia, which consists of “the chain of archipelagos, islands, atolls, and reefs forming the outer bounds of the sheltered oval-shaped coral sea”. This includes the Louisiade archipelago (part of Papua New Guinea), the Bismarck Archipelago (part of Papua New Guinea and the Solomon Islands), and the Santa Cruz Islands (part of the Solomon Islands). The country of Vanuatu is composed of the New Hebrides island chain. New Caledonia is composed of one large island and several smaller chains, including the Loyalty Islands. The nation of Fiji is composed of two main islands, Viti Levu and Vanua Levu, and smaller islands, including the Lau Islands.
The names of islands in Melanesia can be confusing: they have both indigenous and European names. National boundaries sometimes cut across archipelagos. The names of the political units in the region have changed over time, and sometimes have included geographical terms. For example, the island of Makira was once known as San Cristobal, the name given to it by Spanish explorers. It is in the country, Solomon Islands, which is a nation-state and not a contiguous archipelago. The border of Papua New Guinea and the Solomon Islands separates the island of Bougainville from nearby islands like Choiseul, although Bougainville is geographically part of the chain of islands that includes Choiseul and much of the Solomons. In addition to the islands mentioned here, there are many smaller islands and atolls in Melanesia.