The St. Lawrence Iroquoians were Aboriginal people who lived from the 14th century to about 1580 concentrated along the shores of the St. Lawrence River in present-day Quebec and Ontario, Canada, and New York State, United States, although their territory extended east. They spoke Laurentian languages, a branch of the Iroquoian family. They were believed to have numbered up to 120,000 people in 25 nations. However, this much higher estimate of the number Lawrence Iroquoians is disputed. The traditional view is that they disappeared because of late 16th century warfare by the Mohawk nation of the Haudenosaunee, who wanted to control fur trade in the valley. But other possibilities, including climate change, wars with various Algonquin tribes and exposure to European diseases, may have been equally important.
Knowledge about the St. Lawrence Iroquoians has been constructed from the studies of surviving oral accounts of the historical past from the current Native people, writings of the French explorer Jacques Cartier, earlier histories, and anthropologists' and other scholars' work with archaeological and linguistic studies since the 1950s. Archaeological evidence has established this was a people distinct from the other regional Iroquoian peoples, the Five Nations of the Haudenosaunee and the Wendat (Huron). Recent archaeological finds suggest distinctly separate groups may have existed among the St. Lawrence Iroquoians as well.
For years historians and other scholars debated the identity of the Iroquoian cultural group in the St. Lawrence valley which Jacques Cartier and his crew recorded encountering in 1535–36 at Stadacona and Hochelaga. An increasing amount of archaeological evidence since the 1950s has settled some of the debate. Since the 1950s, anthropologists and some historians have used definitive linguistic and archaeological studies to reach consensus that the St. Lawrence Iroquoians were peoples distinct from nations of the Iroquois Confederacy or the Huron. Since the 1990s, they have concluded that there may have been as many as 25 tribes among the St. Lawrence Iroquoians, who numbered about 120,000 people. They lived in the river lowlands and east of the Great Lakes, including in present-day northern New York and New England.