Loch Ness (Scottish Gaelic: Loch Nis) is a large, deep freshwater loch in the Scottish Highlands (57°18′N, 4°27′W) extending for approximately 37 km (23 miles) southwest of Inverness. Its surface is 15.8 metres (52 feet) above sea level. Loch Ness is best known for the alleged sightings of the legendary Loch Ness Monster ("Nessie").

Loch Ness is the second-largest Scottish loch by surface area after Loch Lomond at 56.4 kmē (21.8 sq mi), but due to its great depth is the largest by volume. It contains more fresh water than all that in England and Wales combined. Its deepest point is 230 m (754 feet), deeper than the height of London's BT Tower at 189 m (620 feet).

Loch Ness is the largest body of water on the Great Glen geologic fault, which runs from Inverness in the north to Fort William in the south. The Caledonian Canal, which links the sea at either end of the fault, uses Loch Ness for part of its route.

The loch is one of a series of interconnected, murky bodies of water in Scotland. Its water visibility is exceptionally low due to a high peat content in the surrounding soil. It is the second deepest loch in Scotland, and the UK.

It also acts as the lower storage reservoir for the Foyers pumped-storage hydroelectric scheme, which was the first of its kind in United Kingdom. The turbines were originally used to provide power for a nearby mill, but now electricity is generated and supplied to the National Grid.

The only island on Loch Ness is Cherry Island, visible at its southwestern end, near Fort Augustus. It is a crannog -- an artificial island usually from the Iron Age.

At Drumnadrochit is a Loch Ness Monster exhibition centre, which contains information on the legendary creature. Boat cruises operate from various locations on the loch shore, giving tourists the chance to look for the monster