Moidart is part of the remote and isolated area of Scotland, west of Fort William, known as the Rough Bounds. Moidart itself is almost surrounded by bodies of water. Loch Shiel cuts off the eastern boundary of the district and continues along part of the southern edge. The remainder of the southern edge is cut off by Loch Moidart. The north is cut off by Loch Morar and Loch Ailort.

Loch Shiel is a freshwater loch situated 20 kilometres (12 mi) west of Fort William in the Highland council area of Scotland. At 28 kilometres long it is the 4th longest loch in Scotland, and is the longest to have retained a natural outflow without any regulation of its water level, being 120 m (393 ft) deep. Its nature changes considerably along its length, being deep and enclosed by mountains in the north east and shallow surrounded by bog and rough pasture in the south west, from which end the 4 km River Shiel drains to the sea in Loch Moidart near Castle Tioram.