The Frontenac Axis is an exposed strip of Precambrian rock in Canada and the United States which links the Canadian Shield with the Adirondack mountain range in New York, an extension of the Laurentian mountains of Québec. The axis separates the St. Lawrence Lowlands and the Great Lakes Lowlands. It is an ecoregion of the Mixedwood Plains. It also separates the Canadian Shield and the Lowlands.