Lorentz National Park is an Indonesian national park located in the provinces of Central Papua, Highland Papua and South Papua, in the southwest of western New Guinea. With an area of 25,056&nbsp;km<sup>2</sup> (9,674&nbsp;mi<sup>2</sup>), it is the largest national park in Southeast Asia. In 1999 Lorentz was declared a World Heritage Site by UNESCO.

thumb|upright|right|Park map

An outstanding example of the biodiversity of New Guinea, Lorentz is one of the most ecologically diverse national parks in the world. It is the only nature reserve in the Asia-Pacific region to contain a full altitudinal array of ecosystems ranging through marine areas, mangroves, tidal and freshwater swamp forest, lowland and montane rainforest, subalpine shrub and grassland, alpine tundra, and equatorial glaciers. At , Puncak Jaya (formerly Carstensz Pyramid) is the tallest mountain between the Himalayas and the Andes.

Birdlife International has called Lorentz Park "probably the single most important reserve in New Guinea". It contains five of World Wildlife Fund's "Global 200" ecoregions: Southern New Guinea Lowland Forests; New Guinea Montane Forests; New Guinea Central Range Subalpine Grasslands; New Guinea Mangroves; and New Guinea Rivers and Streams.

Lorentz Park contains many unmapped and unexplored areas, and is certain to contain many species of plants and animals as yet unknown to Western science. Local communities' ethnobotanical and ethnozoological knowledge of the Lorentz biota is also very poorly documented.

The park is named after Hendrikus Albertus Lorentz, a Dutch explorer who passed through the area on his 1909–10 expedition.

Birds

thumb|upright|left|The [[southern crowned pigeon, pictured in a Singapore zoo, is confined to the southern lowland forests of New Guinea.]]

Lorentz National Park has 630 documented species of bird (around 95% of the total number of bird species in Papua) and 123 mammalian species. Birds include two species of cassowary, 31 dove and pigeon species, and 60 species of kingfisher. Six bird species are endemic to the Snow Mountains including the Snow Mountain quail and Snow Mountains robin, 26 species are endemic to the Central Papuan Ranges while three are endemic to the South Papuan Lowlands. Threatened species include the southern cassowary, Alpine woolly rat, southern crowned pigeon, Pesquet's parrot, Salvadori's teal and Macgregor's giant honeyeater.

The mammal species include the long-beaked echidna, short-beaked echidna, and four species of cuscus as well as wallabies, quolls and tree-kangaroos.

Conservation

The first formal protection of a 3,000&nbsp;km<sup>2</sup> core area of the Lorentz landscape was applied by the Dutch Colonial Government in 1919 with the establishment of the Lorentz Nature Monument. In 1978, the Indonesian Government established a Strict Nature Reserve with an area of 21,500&nbsp;km<sup>2</sup>. Lorentz National Park was established in 1997, with a total area of 25,056&nbsp;km<sup>2</sup>, including an eastern extension and coastal and marine areas.

Lorentz National Park was listed as a natural World Heritage Site in 1999, however an area of about 1,500&nbsp;km<sup>2</sup> was excluded from listing due to the presence of mining exploration titles within the park.

As of 2005, there were no park staff or guards assigned to Lorentz. However, the park's success largely depends on local communities' understanding of and support for conservation, rather than external enforcement alone. Several conservation organizations are working in the Lorentz area.

In 2006, the Minister of Forestry established a managing structure for Lorentz National Park, the Lorentz National Park Bureau with headquarters in Wamena. The Bureau became functional only in 2007, and reached a staffing of 44 in mid-2008. However an UNESCO Monitoring Mission in 2008 acknowledged that the capacity of the Bureau was seriously limited due to lack of funding, equipment and experience.