The Seneca ( ; () are a group of Indigenous Iroquoian-speaking people who historically lived south of Lake Ontario, one of the five Great Lakes in North America. Their nation was the farthest to the west within the Six Nations or Iroquois League (Haudenosaunee) in New York before the American Revolution. For this reason, they are called “The Keepers of the Western Door.”

In the 21st century, more than 10,000 Seneca live in the United States, which has three federally recognized Seneca tribes. Two of them are centered in New York: the Seneca Nation of Indians, with five territories in western New York near Buffalo; and the Tonawanda Seneca Nation. The Seneca-Cayuga Nation is in Oklahoma, where their ancestors were relocated from Ohio during the Indian Removal. Approximately 1,000 Seneca live in Canada, near Brantford, Ontario, at the Six Nations of the Grand River First Nation. They are descendants of Seneca who resettled there after the American Revolution, as they had been allies of the British and forced to cede much of their lands.

The tribe's name has no logical connection with the ancient Roman statesmen Seneca the Elder and Seneca the Younger.

History
Seneca oral history states that the tribe originated in a village called Nundawao, near the south end of Canandaigua Lake, at South Hill. Close to South Hill stands the  Bare Hill, known to the Seneca as. Bare Hill is part of the Bare Hill Unique Area, which began to be acquired by the state in 1989. Bare Hill had been the site of a Seneca (or Seneca-ancestral people) fort.

The first written reference to this fort was made in 1825 by the Tuscarora historian David Cusick in his history of the Seneca Indians.

In the early 1920s, the material that made up the Bare Hill fort was used by the Town of Middlesex highway department for road fill.

The Seneca historically lived in what is now New York state between the Genesee River and Canandaigua Lake. The dating of an oral tradition mentioning a solar eclipse yields 1142 AD as the year for the Seneca joining the Iroquois (Haudenosaunee). Some recent archaeological evidence indicates their territory eventually extended to the Allegheny River in present-day northwestern Pennsylvania, particularly after the Iroquois destroyed both the Wenrohronon and Erie nations in the 17th century, who were native to the area. The Seneca were by far the most populous of the Haudenosaunee nations, numbering about four thousand by the seventeenth century.

Seneca villages were located as far east as current-day Schuyler County (e.g. Catherine's Town and Kanadaseaga), south into current Tioga and Chemung counties, north and east into Tompkins and Cayuga counties, and west into the Genesee River valley. The villages were the homes and headquarters of the Seneca. While the Seneca maintained substantial permanent settlements and raised agricultural crops in the vicinity of their villages, they also hunted widely through extensive areas. They also executed far-reaching military campaigns. The villages, where hunting and military campaigns were planned and executed, indicate the Seneca had hegemony in these areas.

Major Seneca villages were protected with wooden palisades. Ganondagan, with 150 longhouses, was the largest Seneca village of the 17th century, while Chenussio, with 130 longhouses, was a major village of the 18th century.

The Seneca has two branches: the western and the eastern. Each branch was individually incorporated and recognized by the Iroquois Confederacy Council. The western Seneca lived predominantly in and around the Genesee River, gradually moving west and southwest along Lake Erie and the Niagara River, then south along the Allegheny River into Pennsylvania. The eastern Seneca lived predominantly south of Seneca Lake. They moved south and east into Pennsylvania and the western Catskill area.

The west and north were under constant attack from their powerful Iroquoian brethren, the Huron (Wyandot) To the South, the Iroquoian-speaking tribes of the Susquehannock (Conestoga) also threatened constant warfare. The Algonquian tribes of the Mohican blocked access to the Hudson River in the east and northeast. In the southeast, the Algonkian tribes of the Lenape people (Delaware, Minnisink and Esopus) threatened war from eastern Pennsylvania, New Jersey and the Lower Hudson.

The Seneca used the Genesee and Allegheny rivers, as well as the Great Indian War and Trading Path (the Seneca Trail), to travel from southern Lake Ontario into Pennsylvania and Ohio (Merrill, Arch. Land of the Senecas; Empire State Books, 1949, pp. 18–25). The eastern Seneca had territory just north of the intersection of the Chemung, Susquehanna, Tioga and Delaware rivers, which converged in Tioga. The rivers provided passage deep into all parts of eastern and western Pennsylvania, as well as east and northeast into the Delaware Water Gap and the western Catskills. The men of both branches of the Seneca wore the same headgear. Like the other Haudenosaunee, they wore hats with dried cornhusks on top. The Seneca wore theirs with one feather sticking up straight.

Traditionally, the Seneca Nation's economy was based on hunting and gathering activities, fishing, and the cultivation of varieties of corn, beans, and squash. These vegetables were the staple of the Haudenosaunee diet and were called "the three sisters" (työhe'hköh). Seneca women generally grew and harvested varieties of the three sisters, as well as gathering and processing medicinal plants, roots, berries, nuts, and fruit. Seneca women held sole ownership of all the land and the homes. The women also tended to any domesticated animals such as dogs and turkeys. 

Seneca men were generally in charge of locating and developing the town sites, including clearing the forest for the production of fields. Seneca men also spent a great deal of time hunting and fishing. This activity took them away from the towns or villages to well-known and productive hunting and fishing grounds for extended amounts of time. These hunting and fishing locations were altered and well maintained to encourage game; they were not simply "wild" lands. Seneca men maintained the traditional title of war sachems within the Haudenosaunee. A Seneca war sachem was in charge of gathering the warriors and leading them into battle.

Seneca people lived in villages and towns. Archaeological excavations indicate that some of these villages were surrounded by palisades because of warfare. These towns were relocated every ten to twenty years  as soil, game and other resources were depleted. During the nineteenth century, many Seneca adopted customs of their immediate American neighbors by building log cabins, practicing Christianity, and participating in the local agricultural economy.

Daily life of the Seneca 
The Seneca traditionally lived in longhouses, which are large buildings that were up to 100 feet long and approximately 20 feet wide. The longhouses were shared among related families and could hold up to 60 people. Hearths were located in the central aisle, and two families shared a hearth. Over time they began to build cabins, similar to those of their American neighbors.

The main form of social organization is the clan, or, nominally each descended from one woman. The Seneca have eight clans: Bear (), Wolf (), Turtle (), Beaver( ), Deer (), Hawk (), Snipe (), and Heron (). The clans are divided into two sides (moieties)the Bear, Wolf, Turtle, and Beaver are the animal side, and the Deer, Hawk, Snipe, and Heron are the bird side.

The Iroquois have a matrilineal kinship system; inheritance and property descend through the maternal line. Women are in charge of the clans. Children are considered born into their mother's clan and take their social status from her family. Their mother's eldest brother was traditionally more of a major figure in their lives than their biological father, who does not belong to their clan. The presiding elder of a clan is called the "clan mother". Despite the prominent position of women in Iroquois society, their influence on the diplomacy of the nation was limited. If the "clan mothers" do not agree with any major decisions made by the chiefs, they can eventually depose them.

Seneca Archery
Arrows from the area are made from split hickory, although shoots of dogwood and Viburnum were used as well. The eastern two feather style of fletching was used, although three radial feathers were also used.

The Smithsonian Institution has an example of a Seneca bow, which was donated 1908. It is made of unbacked hickory, and is  tip to tip. Although the string is missing for the specimen, when strung it would make a good "D" shape with slightly recurved tips, and was obviously made for bigger game. The tips are irregular in shape, which is typical from this region.

Contact with Europeans 

During the colonial period, the Seneca became involved in the fur trade, first with the Dutch and then with the British. This served to increase hostility with competing native groups, especially their traditional enemy, the Huron (Wyandot), an Iro