The Iroquois also known as the Five Nations or the Six Nations and by the autonym Haudenosaunee meaning "people who are building the longhouse"), are an Iroquoian-speaking confederacy of Native Americans and First Nations peoples in northeast North America and Upstate New York. They were known during the colonial years to the French as the "Iroquois League", and later as the "Iroquois Confederacy". The English called them the "Five Nations", including (east to west) the Mohawk, Oneida, Onondaga, Cayuga, and Seneca. After 1722, the Iroquoian-speaking Tuscarora from the southeast were accepted into the confederacy, which became known as the Six Nations.

The Confederacy came about as a result of the Great Law of Peace, said to have been composed by Deganawidah the Great Peacemaker, Hiawatha, and Jigonsaseh the Mother of Nations. For nearly 200 years, the Six Nations/Haudenosaunee Confederacy was a powerful factor in North American colonial policy, with some scholars arguing for the concept of the Middle Ground, in that European powers were used by the Iroquois just as much as Europeans used them. At its peak around 1700, Iroquois power extended from what is today New York State, north into present-day Ontario and Quebec along the lower Great Lakes, upper St. Lawrence, and south on both sides of the Allegheny mountains into present-day Virginia and Kentucky and into the Ohio Valley.

The St. Lawrence Iroquoians, Wendat (Huron), Erie, and Susquehannock, all independent peoples known to the European colonists, also spoke Iroquoian languages. They are considered Iroquoian in a larger cultural sense, all being descended from the Proto-Iroquoian people and language. Historically, however, they were competitors and enemies of the Iroquois League nations.

In 2010, more than 45,000 enrolled Six Nations people lived in Canada, and over 81,000 in the United States

Tee Yee Neen Ho Ga Ron Emperour of the Six Nations. Sa Ga Yeath Lua Pieth Ton King of the Maguas. Eton Oh Koam King of the River Nation. Ho Nee Yeath Tan No Ron King of the Generethgarich 

The Iroquois Confederacy is believed to have been founded by the Great Peacemaker at an unknown date estimated between 1450 and 1660, bringing together five distinct nations in the southern Great Lakes area into "The Great League of Peace". Other research, however, suggests the founding occurred in 1142. Each nation within this Iroquoian confederacy had a distinct language, territory, and function in the League.

The League is governed by a Grand Council, an assembly of fifty chiefs or sachems, each representing a clan of a nation.

When Europeans first arrived in North America, the Haudenosaunee (Iroquois League to the French, Five Nations to the British) were based in what is now central and west New York State including the Finger Lakes region, occupying large areas north to the St. Lawrence River, east to Montreal and the Hudson River, and south into what is today northwestern Pennsylvania. At its peak around 1700, Iroquois power extended from what is today New York State, north into present-day Ontario and Quebec along the lower Great Lakes, upper St. Lawrence, and south on both sides of the Allegheny Mountains into present-day Virginia and Kentucky and into the Ohio Valley. From east to west, the League was composed of the Mohawk, Oneida, Onondaga, Cayuga, and Seneca nations. In about 1722, the Iroquoian-speaking Tuscarora joined the League, having migrated northwards from the Carolinas after a bloody conflict with white settlers. A shared cultural background with the Five Nations of the Iroquois (and sponsorship from the Oneida) led the Tuscarora to become accepted as the sixth nation in the confederacy in 1722; the Iroquois became known afterwards as the Six Nations.

Other independent Iroquoian-speaking peoples, such as the Erie, Susquehannock, Huron (Wendat) and Wyandot, lived at various times along the St. Lawrence River, and around the Great Lakes. In the American Southeast, the Cherokee were an Iroquoian-language people who had migrated to that area centuries before European contact. None of these were part of the Haudenosaunee League. Those on the borders of Haudenosaunee territory in the Great Lakes region competed and warred with the nations of the League.

French, Dutch and English colonists, both in New France (Canada) and what became the Thirteen Colonies, recognized a need to gain favour with the Iroquois people, who occupied a significant portion of lands west of the colonial settlements. Their first relations were for fur trading, which became highly lucrative for both sides. The colonists also sought to establish friendly relations to secure their settlement borders.

For nearly 200 years, the Iroquois were a powerful factor in North American colonial policy. Alliance with the Iroquois offered political and strategic advantages to the European powers, but the Iroquois preserved considerable independence. Some of their people settled in mission villages along the St. Lawrence River, becoming more closely tied to the French. While they participated in French-led raids on Dutch and English colonial settlements, where some Mohawk and other Iroquois settled, in general, the Iroquois resisted attacking their own peoples.

The Iroquois remained a large politically united Native American polity until the American Revolution, when the League kept its treaty promises to the British Crown. After their defeat, the British ceded Iroquois territory without consultation, and many Iroquois had to abandon their lands in the Mohawk Valley and elsewhere and relocate to the northern lands retained by the British. The Crown gave them land in compensation for the five million acres they had lost in the south, but it was not equivalent to earlier territory.

Modern scholars of the Iroquois distinguished between the League and the Confederacy. According to this interpretation, the Iroquois League refers to the ceremonial and cultural institution embodied in the Grand Council, which still exists. The Iroquois Confederacy was the decentralized political and diplomatic entity that emerged in response to European colonization, which was dissolved after the British defeat in the American Revolutionary War. Today's Iroquois/Six Nations people do not make any such distinction, use the terms interchangeably, but prefer the name Haudenosaunee Confederacy.

After the migration of a majority to Canada, the Iroquois remaining in New York were required to live mostly on reservations. In 1784, a total of 6,000 Iroquois faced 240,000 New Yorkers, with land-hungry New Englanders poised to migrate west. "Oneidas alone, who were only 600 strong, owned six million acres, or about 2.4 million hectares. Iroquoia was a land rush waiting to happen." By the War of 1812, the Iroquois had lost control of considerable territory.

 Chas. C. Chapman & Co., pub 

Previous research, containing the discovery of Iroquois tools and artifacts, suggests that the origin of the Iroquois was in Montreal, Canada, near the St. Lawrence River. After an unsuccessful rebellion, they were driven out of Quebec to New York.

Knowledge of Iroquois history stems from Haudenosaunee oral tradition, archaeological evidence, accounts from Jesuit missionaries, and subsequent European historians. Historian Scott Stevens credits the early modern European value of written sources over oral tradition as contributing to a racialized, prejudiced perspective about the Iroquois through the 19th century. The historiography of the Iroquois people is a topic of much debate, especially regarding the American colonial period.

French Jesuit accounts of the Iroquois portrayed them as savages lacking government, law, letters, and religion. However the Jesuits made considerable effort to study their languages and cultures, and some came to respect them. A source of confusion for European sources, coming from a patriarchal society, was the matrilineal kinship system of Iroquois society and the related power of women. The Canadian historian D. Peter MacLeod wrote about the Canadian Iroquois and the French in the time of the Seven Years' War:

Most critically, the importance of clan mothers, who possessed considerable economic and political power within Canadian Iroquois communities, was blithely overlooked by patriarchal European scribes. Those references that do exist, show clan mothers meeting in council with their male counterparts to make decisions regarding war and peace and joining in delegations to confront the Onontio [the Iroquois term for the French governor-general] and the French leadership in Montreal, but only hint at the real influence wielded by these women.

Eighteenth-century English historiography focuses on the diplomatic relations with the Iroquois, supplemented by such images as John Verelst's Four Mohawk Kings, and publications such as the Anglo-Iroquoian treaty proceedings printed by Benjamin Franklin. A persistent 19th and 20th-century narrative casts the Iroquois as "an expansive military and political power ... subjugated their enemies by violent force and for almost two centuries acted as the fulcrum in the balance of power in colonial North America".

Historian Scott Stevens noted that the Iroquois themselves began to influence the writing of their history in the 19th century, including Joseph Brant (Mohawk), and David Cusick (Tuscarora, 1780–1840). John Arthur Gibson (Seneca, 1850–1912) was an important figure of his generation in recounting versions of Iroquois history in epics on the Peacemaker. Notable women historians among the Iroquois emerged in the following decades, including Laura "Minnie" Kellog (Oneida, 1880–1949) and Alice Lee Jemison (Seneca, 1901–1964

Many Iroquois (mostly Mohawk) and Iroquois-descended Métis people living in Lower Canada (primarily at Kahnawake) took employment with the Montreal-based North West Company during its existence from 1779 to 1821 and became voyageurs or free traders working in the North American fur trade as far west as the Rocky Mountains. They are known to have settled in the area around Jasper's House and possibly as far west as the Finlay River and north as far as the Pouce Coupe and Dunvegan areas, where they founded new Aboriginal communities which have persisted to the present day claiming either First Nations or Métis identity and indigenous rights. The Michel Band, Mountain Métis, and Aseniwuche Winewak Nation of Canada in Alberta and the Kelly Lake community in British Columbia all claim Iroquois ancestry.