The Portuguese and the Spanish were the first Europeans to know of New Guinea, through sightings and landings early in the 1500's. More than a century and a half later the Dutch East India Company acquired rights in the western half of the island from the Sultan of Ternate in the Moluccas. The Dutch annexed western New Guinea in 1828. In 1884 the eastern half of New Guinea was divided between Great Britain and Germany. The British section, later the Territory of Papua, became British New Guinea and was placed under Australian control in 1906. The German part, later Northeast New Guinea, became Kaiser Wilhelmsland. Kaiser Wilhelmsland was occupied by Australian forces during World War I. In 1920 it was made part of a League of Nations territory mandated to Australia. This territory, including the Bismarck Archipelago and the northern Solomon Islands, was designated the Trust Territory of New Guinea by the United Nations in 1946. In 1949 Australia organized the trust territory and the Territory of Papua into one administrative unit, later named Papua New Guinea.

In 1963, after a bitter dispute, the Dutch relinquished control of western New Guinea to Indonesia. It was renamed West Irian and formally annexed by Indonesia in 1969. In 1973 West Irian was renamed Irian Jaya. In the same year, Australia granted internal self-government to Papua New Guinea, and in 1975 it granted complete independence. The island was hit a by a tsunami in 1999 that killed more than 2,000 people.