Metoac is an erroneous term used by some to group together the Munsee-speaking Lenape (west), Quiripi-speaking Unquachog (center), and Pequot-speaking Montaukett (east) American Indians on what is now Long Island in New York state. The term was invented by amateur anthropologist and US Representative Silas Wood in the mistaken belief that the various native settlements on the island each comprised distinct tribes.

Instead, Indian peoples on Long Island at the time of European contact came from only two major language and cultural groups of the many Algonquian peoples who occupied Atlantic coastal areas from present-day Canada through the American South. The bands on Long Island in the west were part of the Lenape. Those to the east were culturally and linguistically connected to tribes of New England across Long Island Sound, such as the Pequot. Wood (and earlier colonial settlers) often confused Indian place names, by which the bands were known, with the names for different tribes living there.

Many of the place names that the Lenape and Pequot populations used to refer to their villages and communities were adopted by English settlers and are still in use today. The Shinnecock Indian Nation, based in part of what is now Southampton, New York in Suffolk County, has gained federal recognition as a tribe and has a reservation there.

"Metoac" as a collective term may have been derived by Wood from metau-hok, the Algonquian word for the rough periwinkle, the shell of which small sea snail was used to make wampum, a means of exchange which played an important role in the culture and economy of the region before and after the arrival of Europeans.^{[citation needed]}

The Native American population on Long Island has been estimated at 10,000 at the time of first contact with Europeans. They belonged to two major nations and spoke two languages within the Algonquian language group, reflecting their different connections to mainland peoples. Native Americans in the west and in the central part of Long Island were more closely associated with bands of the same people in southwestern Connecticut, Eastern Pennsylvania, Lower Hudson Valley in New York, New Jersey, and Delaware. These people spoke one of the R-dialects of the Lenape language group. Those Native Americans who lived on the east end of the island were more closely related to the Pequot of eastern Connecticut and the other Algonquian language group located around Long Island Sound. They spoke a Y-dialect of the Mohegan-Montauk-Narragansett language.

European colonization of the region began in the 1620s, with Dutch colonists congregating around the lower Hudson and western Long Island. The Dutch attempted to establish jurisdiction from New Amsterdam over the western portion of Long Island (including what are now the New York City boroughs of Brooklyn and Queens).

The Pequot War (1634–1638) in southern New England and Kieft's War (1643–1645) in the New York metropolitan area were two major conflicts between the indigenous peoples and the colonists. Exposure to new Eurasian infectious diseases, such as measles and smallpox, dramatically reduced the numbers of Native Americans on Long Island.^{[citation needed]} In addition, some Native American settlements on Long Island migrated away under pressure from European encroachment. ^{[citation needed]} By 1659, their population was reduced to less than 500.^{[citation needed]}

By this time, Samson Occom had persuaded many survivors to join the Brothertown Indians in western upstate New York, where the Oneida people of the Iroquois Confederacy shared their reservation for several years. ^{[citation needed]}