The Sentinelese (also called the Sentineli or North Sentinel Islanders) are the indigenous people of North Sentinel Island in the Andaman Islands of India. One of the Andamanese peoples, they resist contact with the outside world, and are among the last people to remain virtually untouched and uncontacted by modern civilisation.

The Sentinelese maintain an essentially hunter-gatherer society subsisting through hunting, fishing, and collecting wild plants. There is no evidence of either agricultural practices or methods of producing fire. The Sentinelese language remains unclassified and is not mutually intelligible with the Jarawa language of their nearest neighbors. The Sentinelese are designated as a Scheduled Tribe.

The precise population of the Sentinelese is not known.

Estimates range from fewer than 40, through a median of around 250, and up to a maximum of 500.

In 2001, Census of India officials recorded 39 individuals (21 males and 18 females); however, out of necessity this survey was conducted from a distance and almost certainly does not represent an accurate figure for the population which ranges over the 59.67 km 2 (14,700 acres) island. ^[46] The 2011 Census of India recorded only 15 individuals (12 males and three females). Any medium- or long-term effect on the Sentinelese population arising from the 2004 Indian Ocean earthquake and resulting tsunami is not known, other than the confirmation obtained that they had survived the immediate aftermath.

The Sentinelese and other indigenous Andamanese peoples are frequently described as negritos, a term which has been applied to various widely separated peoples in Southeast Asia, such as the Semang of the Malay Peninsula, the Aeta of the Philippines archipelago, as well as to other peoples in Australia including indigenous populations of Tasmania. The defining characteristics of these "negrito" peoples (who are not a monophyletic group) include a comparatively short stature, dark skin, and afro-textured hair.

Although no close contacts have been established, author Heinrich Harrer described one man as being 1.6 metres (5 ft 3 in) tall and apparently left handed.

Most of what is known about Sentinelese material culture is based on observations during contact attempts in the late 20th century. The Sentinelese maintain an essentially hunter-gatherer society, obtaining their subsistence through hunting, fishing, and collecting wild plants; there is no evidence of any agricultural practices.

Their dwellings are either shelter-type huts with no side walls and a floor sometimes laid out with palms and leaves, which provide enough space for a family of three or four and their belongings, or larger communal dwellings which may be some 12 square metres (130 sq ft) and are more elaborately constructed, with raised floors and partitioned family quarters.

Advanced metalwork is unknown, as raw materials on the island are extremely rare. It has been observed, however, that they have made adroit use of metal objects which have washed up or been left behind on their shores, having some ability at cold smithing and sharpening iron and incorporating it into weapons and other items. For example, in the late 1980s two international container ships ran aground on the island's external coral reefs; the Sentinelese retrieved several items of iron from the vessels.

The 1880 British expedition to the island led by Maurice Vidal Portman reported that "their methods of cooking and preparing their food resemble those of the Öngés, not those of the aborigines of the Great Andaman."

Their weaponry consists of javelins and a type of flatbow. At least three varieties of arrows, apparently for fishing and hunting, and untipped ones for shooting warning shots, have been documented. Fishing arrows have a number of forward-pointing prongs; hunting arrows have ovoid arrowheads, the latter two as well as their associated barbs below the tip made from iron. The arrows are over 1 m (3 ft) long. The harpoon- or javelin-type arrows are nearly half as long again, about the same length as the bows (over 3 m (10 ft)), and can also be thrown or used for stabbing, but the latter probably only rarely.

For catching large fish, a harpoon is used which is similar in design to the fishing arrows, but nearly 2.5 m (8 ft) long.

Knives are also known, but it is unclear to what extent the Sentinelese fashion them themselves.

Known tools include adzes, pounding and smithing stones, and various finely or coarsely woven baskets for small-grained or larger goods, as well as bamboo and wooden containers. Fires are maintained as embers inside dwellings, possibly assisted by resin torches. There exist fishing nets and basic outrigger canoes used for fishing and collecting shellfish from the lagoon but not for open-sea excursions.

Food consists primarily of plants gathered in the forest, coconuts, which are frequently found on the beaches as flotsam, pigs, and, presumably, other wildlife (which apart from sea turtles is limited to some smaller birds and invertebrates). Wild honey is known to be collected and the Sentinelese use a kind of rake to pull down branches to gather fruit or nuts, such as sapodilla and pandanus.

In January 1880, an armed British expedition to the island led by 20-year-old Maurice Vidal Portman, the local colonial administrator, arrived to conduct a survey of the island, and to take a prisoner, in accordance with British policy regarding unwelcoming tribes at the time, which was to kidnap a member of the tribe, treat them well and give them gifts, and release them back to the tribe, hoping to demonstrate friendliness. Portman's expedition of the island is believed to be the first by outsiders. While the Sentinelese tended to disappear into the jungle whenever outsiders were spotted approaching, Portman's expedition found an elderly couple and four children after several days. They were taken prisoner and brought to Port Blair. The elderly couple became ill and died, probably from contracting diseases to which they did not have immunity. The four children were returned to the island, given gifts, and released. The children then disappeared into the jungle. After this incident, the British did not try to contact the Sentinelese again and instead focused on other tribes.

In 1967, the Indian government began a series of "Contact Expeditions" to the island.

The program was managed by the Director of Tribal Welfare and anthropologist T. N. Pandit. The first expedition, headed by Pandit, included armed police and naval officers. The Sentinelese retreated into the jungle, and the expedition failed to make contact with any of them. During these expeditions, an Indian Navy vessel would anchor outside the coral reefs and send small boats to approach the beaches, and while keeping a distance, the crew would drop various gifts into the water to wash up on shore. If the Sentinelese fled for the jungle, the parties might land on shore and drop off the gifts before leaving.

On 29 March 1970, a research party of Indian anthropologists, which included Pandit, found themselves cornered on the reef flats between North Sentinel and Constance Island.

An eyewitness recorded the following from his vantage point on a boat lying off the beach:

In early 1974, a National Geographic film crew went to the island, in what was one of the most unsuccessful expeditions made on the island. North Sentinel was visited by a team of anthropologists filming a documentary, Man in Search of Man. The team was accompanied by armed police officers and a National Geographic photographer. When the motorised boat broke through the barrier reefs, locals emerged from the jungle. The Sentinelese responded with a curtain of arrows. The boat landed at a point on the coast out of range of the arrows and the police (dressed in jackets with padded armour) landed and left gifts in the sand: a miniature plastic car, some coconuts, a live pig tied, a doll, and aluminium cookware. The policemen returned to the boat and waited to see the locals' reaction to the gifts. The reaction was to launch another round of arrows, one of which struck the documentary's director in the left thigh. The man who wounded the director withdrew and laughed proudly, sitting in the shade while others speared, then buried, the pig and the doll. Afterwards, everyone left, taking with them only the coconuts and aluminium cookware.

There were documented occasions (one in 1980) when Onge-speaking individuals were taken to North Sentinel Island in order to attempt communication, resulting in brief and hostile exchanges, during which they were unable to recognise any of the language spoken by the inhabitants.

On August 2, 1981, the MV Primrose ran aground on North Sentinel Island, stranding twenty-eight sailors.

The next morning, the captain of the ship broadcast urgent messages indicating that natives were on the verge of attacking the vessel with arrows and spears.

^[34] After being shipwrecked for two weeks, all crew and passengers on the ship were successfully evacuated by helicopter.

In the early 1990s, the Sentinelese began allowing the boats to come closer to the shore, and sometimes greeted them unarmed.

However, after a few minutes, the Sentinelese would ward them off by making menacing gestures and firing arrows without arrowheads.

In 1996, the Indian government ended the "Contact Expeditions" following a series of hostile encounters resulting in several deaths in a similar programme practised with the Jarawa people of South and Middle Andaman Islands and because of the danger of introducing diseases.

The Sentinelese appear to have emerged relatively unscathed from the 2004 Indian Ocean tsunami, apparently managing to reach high ground. Three days following the tsunami, an Indian naval helicopter was sent to check on them and drop food on the beach. It was warned away by a Sentinelese warrior who emerged from the jungle and brandished a bow and arrow.

In 2006, Sentinelese archers killed two fishermen who were fishing illegally for mud crabs within range of the island. Their boat's improvised anchor failed to prevent it from being carried away by currents while they were asleep. The boat drifted into the shallows of the island, where they were killed. An Indian Coast Guard helicopter that was sent to retrieve the bodies was driven off by Sentinelese warriors, who fired a volley of arrows.

Their island is legally a part of, and administered by, the Indian Union Territory of Andaman and Nicobar Islands. In practice, however, the Sentinelese exercise complete sovereignty over their affairs and the involvement of the Indian authorities is restricted to occasional monitoring, ever more infrequent and brief visits, and generally discouraging any access or approaches to the island. The possibility of future contact, whether violent or non-violent (armed or unarmed) has been discussed by various organisations and nations.