The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. Those islands lying south of the tropic of Cancer are traditionally grouped into three divisions: Melanesia, Micronesia and Polynesia.

Pacific islands are also sometimes collectively called Oceania (although Oceania is sometimes defined as also including Australasia and the Malay Archipelago),

• Melanesia means black islands. These include New Guinea (the largest Pacific island, which is divided into the sovereign nation of Papua New Guinea and the Indonesian provinces of Maluku, Papua and West Papua), New Caledonia, Zenadh Kes (Torres Strait Islands), Vanuatu, Fiji, and the Solomon Islands.
• Micronesia means small islands. These include the Marianas, Guam, Wake Island, Palau, the Marshall Islands, Kiribati, Nauru, and the Federated States of Micronesia. Most of these lie north of the equator.
• Polynesia means many islands. These include New Zealand, the Hawaiian Islands, Rotuma, the Midway Islands, Samoa, American Samoa, Tonga, Tuvalu, the Cook Islands, French Polynesia, and Easter Island. It is the largest of the three zones.

The region's islands are classified into two groups, high islands and low islands. Volcanoes form high islands, which generally can support more people and have a more fertile soil. Low islands are reefs or atolls, and are relatively small and infertile. Melanesia, the most populous of the three regions, contains mainly high islands, while most of Micronesia and Polynesia are low islands.