The Iroquois are an Iroquoian-speaking confederacy of First Nations peoples in northeast North America/Turtle Island. The English called them the Five Nations, comprising the Mohawk, Oneida, Onondaga, Cayuga, and Seneca. After 1722, the Iroquoian-speaking Tuscarora people 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 were 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 Iroquois subsequently created a highly egalitarian society. One British colonial administrator declared in 1749 that the Iroquois had "such absolute Notions of Liberty that they allow no Kind of Superiority of one over another, and banish all Servitude from their Territories". As raids between the member tribes ended and they directed warfare against competitors, the Iroquois increased in numbers while their rivals declined. The political cohesion of the Iroquois rapidly became one of the strongest forces in 17th- and 18th-century northeastern North America.

The League's council of fifty ruled on disputes and sought consensus. However, the confederacy did not speak for all five tribes, which continued to act independently and form their own war bands. Around 1678, the council began to exert more power in negotiations with the colonial governments of Pennsylvania and New York, and the Iroquois became very adroit at diplomacy, playing off the French against the British as individual tribes had earlier played the Swedes, Dutch, and English.