West Papua (Indonesian: Papua Barat; formerly West Irian Jaya or Irian Jaya Barat) is a province of Indonesia on the western end of the island of New Guinea. It covers the Bird's Head (or Doberai) Peninsula and surrounding islands.

West Papua was created from the western portion of Papua province in February 2003. The split remains controversial. Supporters, including those in the central government in Jakarta and immigrants to Papua from elsewhere in Indonesia, argue that the creation of the new province will help ensure the efficient management of resources and fair distribution of services. The split is widely opposed in Papua itself, where it is viewed as a violation of special autonomy laws governing Papua, and as an effort to quell the Papuan separatist movement (see History of Western New Guinea). In November 2004, an Indonesian court agreed that the split violated Papua's autonomy laws. However, the court ruled that because the new province had already been created, it should remain separate from Papua. The ruling also prohibited the creation of another proposed province, Central Irian Jaya, because the split was not yet completed.

A vital tropical rainforest with the tallest tropical trees and vast biodiversity, Papua's known forest fauna includes marsupials (including possums, wallabies, tree-kangaroos, cuscuses), other mammals (including the endangered Long-beaked Echidna), many bird species (including birds of paradise, cassowaries, parrots, cockatoos), the world's longest lizards (Papua monitor) and the world's largest butterflies. The island has an estimated 16,000 species of plant, 124 genera of which are endemic. The extensive waterways and wetlands of Papua are also home to salt and freshwater crocodile, tree monitors, flying foxes, osprey, bats and other animals; while the equatorial glacier fields remain largely unexplored. In February 2006, a team of scientists exploring the Foja Mountains, Sarmi, discovered numerous new species of birds, butterflies, amphibians, and plants, including a species of rhododendron which may have the largest bloom of the genus. Ecological threats include logging-induced deforestation, forest conversion for plantation agriculture (especially oil palm), smallholder agricultural conversion, the introduction and potential spread of non-native alien species such as the Crab-eating Macaque which preys on and competes with indigenous species, the illegal species trade, and water pollution from oil and mining operations. Papua's ancient rain forests have recently come under an even greater threat of deforestation after the Chinese government has placed an order of 1 billion US dollar or 800,000 cubic meters of the threatened merbau (intsia spp) rainforest timbers, to be used in constructions for the 2008 Summer Olympics.