The Nene, also known as Nēnē and Hawaiian Goose, (Branta sandvicensis) is a species of goose endemic to the Hawaiian Islands. The official bird of the state of Hawaiʻi, the Nene is exclusively found in the wild on the islands of Oahu, Maui, Kauaʻi and Hawaiʻi. The Hawaiian name Nēnē comes from its soft call. The species name sandvicensis refers to the Sandwich Islands, an old name for the Hawaiian Islands.

The Nene evolved from the Canada Goose (Branta canadensis), which most likely arrived on the Hawaiian islands about 500,000 years ago, shortly after the island of Hawaiʻi was formed. This ancestor is the progenitor of the Nene as well as the prehistoric Giant Hawaiʻi Goose and Nēnē-nui (Branta hylobadistes). The Nēnē-nui was larger than the Nene, varied from flightless to flighted depending on the individual, and inhabited the island of Maui. Similar fossil geese found on Oʻahu and Kauaʻi may be of the same species. The Giant Hawaiʻi Goose was restricted to the island of Hawaiʻi and measured 1.2 metres (3.9 ft) in length with a mass of 8.6 kilograms (19 lb), making it more than four times larger than the Nene. It is believed that the herbivorous Giant Hawaiʻi Goose occupied the same ecological niche as the goose-like ducks known as moa-nalo, which were not present on the Big Island.

The Nene is a medium-sized goose at 41 centimetres (16 in) tall. Although they spend most of their time on the ground, they are capable of flight, with some individuals flying daily between nesting and feeding areas. Females have a mass of 1.525–2.56 kilograms (3.36–5.64 lb), while males average 1.695–3.05 kilograms (3.74–6.72 lb), 11% larger than females. Adult males have a black head and hindneck, buff cheeks and heavily furrowed neck. The neck has black and white diagonal stripes. Aside from being smaller, the female Nene is similar to the male in colouration. The adult's bill, legs and feet are black. It has soft feathers under its chin. Goslings resemble the male, but are a duller brown and with less demarcation between the colours of the head and neck, and striping and barring effects are much reduced. The bill, legs and feet are the same as for the adult. Its strong toes are padded and have reduced webbing, an adaptation that allows it to swiftly traverse rough terrain such as lava plains.

The Nene could at one time be found on the islands of Hawaiʻi, Maui, Kahoʻolawe, Lānaʻi, Molokaʻi, and Kauaʻi. Today, its range is restricted to Hawaiʻi, Maui, Molokaʻi, and Kauaʻi. The Nene is an inhabitant of shrubland, grassland, coastal dunes, and lava plains, and related anthropogenic habitats such as pasture and golf courses from sea level to as much as 2,400 metres (7,900 ft). Some populations migrated between lowland breeding grounds and montane foraging areas. The Nene is a herbivore that will either graze or browse, depending on the availability of vegetation. Food items include the leaves, seeds, fruit, and flowers of grasses and shrubs.

The Nene is the world's rarest goose. It is believed that it once was common, with approximately 25,000 Hawaiian Geese living in Hawaiʻi when Captain James Cook arrived in 1778. However, hunting and introduced predators, such as Small Asian Mongooses, pigs, and cats, reduced the population to 30 birds by 1952. Nevertheless, this species breeds well in captivity, and has been successfully re-introduced; in 2004, it was estimated that there were 800 birds in the wild, as well as 1000 in wildfowl collections and zoos The nature reserve WWT Slimbridge, in England, was instrumental in the successful breeding of Hawaiian Geese in captivity.