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 St. Lawrence River is a large international river in the middle latitudes of North America connecting the Great Lakes to the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrence, traversing Ontario and Quebec in Canada and New York in the United States. A section of the river demarcates the Canada–U.S. border.