A narrow loch in the Lochaber district of Highland Council Area, Loch Oich is situated in the Great Glen between Loch Lochy and Loch Ness where it forms the summit level of the Caledonian Canal. It is 4 miles (6½ km) long and no more than a half-mile (1 km) wide and is fed from the west by the River Garry which enters the loch near the settlement of Invergarry. Loch Oich is connected by the River Oich to Loch Ness which lies 7 miles (11 km) to the northeast.