There are at least 3,223 named lakes and reservoirs in Montana. The following list contains lists of lakes and reservoirs in Montana by county.
A lake is a terrain feature (or physical feature), a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is not global). Another definition is a body of fresh or salt water of considerable size that is surrounded by land. On Earth a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond.[1][2]
A reservoir (etymology from French réservoir a "storehouse [3]) is an artificial lake used to store water. Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such a brickwork or cast concrete. Swimming, fishing, and/or boating are permitted in some of these lakes, but not all.
any relatively large body of slowly moving or standing water that occupies an inland basin of appreciable size. Definitions that precisely distinguish lakes, ponds, swamps, and even rivers and other bodies of nonoceanic water are not well established. It may be said, however, that rivers and streams are relatively fast moving; marshes and swamps contain relatively large quantities of grasses, trees or shrubs; and ponds are relatively small in comparison to lakes. Geologically defined, lakes are temporary bodies of water.
a body of fresh or salt water of considerable size, surrounded by land.