Which lake is the deepest in the United Kingdom?

The deepest lake in the United Kingdom is Loch Morar. This freshwater loch in Scotland’s Highland region reaches a maximum depth of about 310 metres, or 1,017 feet.

Loch Morar occupies a long glacial basin in Lochaber. Ice shaped and overdeepened the valley during the Quaternary glaciations, leaving a lake approximately 18.8 kilometres long. Despite its great depth, it has a relatively small surface area of about 26.7 square kilometres and is only around nine metres above sea level.

Loch Morar is also unusually clear and nutrient-poor, a condition described as oligotrophic. Its short outflow, the River Morar, runs westward toward the sea. The loch is the fifth-largest in Scotland by surface area, but depth—not area—is what gives it this particular record.

Lough Neagh is a common alternative because it is the United Kingdom’s largest lake by surface area. Loch Ness is another frequent mix-up: it contains more water by volume, but it is not as deep as Loch Morar. The loch also has local folklore about a mysterious creature called Mòrag.