The St. Lawrence Iroquoians were an Iroquoian Indigenous people who existed until about the late 16th century. They concentrated along the shores of the St. Lawrence River in present-day Quebec and Ontario, Canada, and in the American states of New York and northernmost Vermont. They spoke Laurentian languages, a branch of the Iroquoian family.
The Pointe-à-Callière Museum estimated their numbers as 120,000 people in 25 nations occupying an area of 230,000 square kilometres (89,000 sq mi). However, many scholars believe that this estimate of the number of St. Lawrence Iroquoians and the area they controlled is too expansive. The current archaeological evidence indicates that the largest known village had a population of about 1,000 and their total population was 8,000–10,000. The traditional view is that they disappeared because of late 16th-century warfare by the Mohawk nation of the Haudenosaunee or Iroquois League, which wanted to control trade with Europeans in the valley.