The Great Lakes (French: Grands Lacs), also called the Great Lakes of North America or the Laurentian Great Lakes, are a series of large interconnected freshwater lakes in the upper mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. They are Lakes Superior, Michigan, Huron, Erie, and Ontario and are in general on or near the Canada–United States border. Hydrologically, there are four lakes, because lakes Michigan and Huron join at the Straits of Mackinac. The Great Lakes Waterway enables travel by water between the lakes.
The Great Lakes are the largest group of freshwater lakes on Earth by total area, and are second-largest by total volume, containing 21% of the world's surface fresh water by volume. The total surface is 94,250 square miles (244,106 km2), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km3), slightly less than the volume of Lake Baikal (5,666 cu mi or 23,615 km3, 22–23% of the world's surface fresh water). Because of their sea-like characteristics, such as rolling waves, sustained winds, strong currents, great depths, and distant horizons, the five Great Lakes have long been called inland seas. By surface area, Lake Superior is the second-largest lake in the world, and is the largest freshwater lake. Lake Michigan is the largest lake that is entirely within one country.
The Great Lakes began to form at the end of the Last Glacial Period around 14,000 years ago, as retreating ice sheets exposed the basins they had carved into the land, which then filled with meltwater. The lakes have been a major source for transportation, migration, trade, and fishing, serving as a habitat to many aquatic species in a region with much biodiversity. The surrounding region is called the Great Lakes region, which includes the Great Lakes Megalopolis.