Loch Ròg or Loch Roag is a large sea loch on the west coast of Lewis, Outer Hebrides. It is broadly divided into East Loch Roag and West Loch Roag with other branches which include Little Loch Roag. The loch is dominated by the only inhabited island Great Bernera and East Loch Roag is actually referred to as Loch Bernera on early maps, most notably Murdoch MacKenzie's original Admiralty Chart from 1776. The use of west and east to differentiate the sections of the loch appear from the original Ordnance Survey in the 19th century.