Lake Champlain ( sham-PLAYN; French: Lac Champlain) is a natural freshwater lake in North America. It mostly lies between the US states of New York and Vermont, but also extends north into the Canadian province of Quebec.

The New York portion of the Champlain Valley includes the eastern portions of Clinton County and Essex County. Most of this area is part of the Adirondack Park. There are recreational facilities in the park and along the relatively undeveloped coastline of Lake Champlain. The cities of Plattsburgh, New York, and Burlington, Vermont, are on the lake's western and eastern shores, respectively, and the town of Ticonderoga, New York, is in the region's southern part. The Quebec portion is in the regional county municipalities of Le Haut-Richelieu and Brome-Missisquoi. There are a number of islands in the lake; the largest include Grand Isle, Isle La Motte and North Hero: all part of Grand Isle County, Vermont.

Because of both Lake Champlain's connection to the St. Lawrence Seaway via the Richelieu River and the existence of the Champlain Canal, Lake Champlain is sometimes referred to as "The Sixth Great Lake."