The Loch Ness Monster (Scottish Gaelic: Uilebheist Loch Nis), affectionately known as Nessie, is a creature in Scottish folklore that is said to inhabit Loch Ness in the Scottish Highlands. It is often described as large, long-necked, and with one or more humps protruding from the water. Popular interest and belief in the creature has varied since it was brought to worldwide attention in 1933. Evidence of its existence is anecdotal, with a number of disputed photographs and sonar readings.

The scientific community regards the Loch Ness Monster as a phenomenon without biological basis, explaining sightings as hoaxes, wishful thinking, and the misidentification of mundane objects. The pseudoscience and subculture of cryptozoology has placed particular emphasis on the creature.