Please see also Lough

A January view across Loch Lomond, towards Ben Lomond

Loch is Scottish Standard English and a name for bodies of water which are either:

• a lake or;
• a sea loch, which may be perceived also as a firth, fjord, estuary, bay or sea inlet.

This name for a body of water is Gaelic in origin and is applied to most lakes in Scotland and to many sea inlets in the west of Scotland. To a very limited extent it is applied also to bodies of water in Northern Ireland and Ulster. Lough, the word's more Anglicised form, is used throughout the island of Ireland.

Although there is no strict size definition, a small loch is often known as a lochan.

Perhaps the most famous Scottish loch is Loch Ness, although there are other large examples such as Loch Awe, Loch Lomond and Loch Tay. For a full list, see list of Scottish lochs.

Examples of sea lochs include Loch Long, Loch Fyne, Loch Linnhe, Loch Eriboll.

Some new reservoirs for hydroelectric schemes have been given names faithful to the names for natural bodies of water - for example: the Loch Sloy scheme, and Lochs Lagan and Treig (which form part of the Lochaber hydroelectric scheme near Fort William). Other expanses are simply called reservoirs, eg: Blackwater Reservoir above Kinlochleven.

Scotland has only one natural water body actually called a lake, the Lake of Menteith, an Anglicisation of the Scots Laich o Menteith meaning a low-lying bit of land in Menteith, and applied to the loch there because of the similarity of the sounds of the words laich and lake. Although, it does look more like an English lake than a Scottish loch, mostly surrounded by low-lying land rather than hills.