Fionn Loch is a remote deep freshwater loch. It is oriented roughly NNWâÂÂSSE and is about 7 km long and around 1 km wide. It lies four miles north-east of, and roughly parallel to, Loch Maree, 4.5 miles south-east of Aultbea and 6 miles east of Poolewe in Wester Ross.
At the southern end of Fionn Loch is Dubh Loch ("White Loch" and "Black Loch"). This is a small loch that is separated from Fionn Loch by a shallow bar about 100 yards long, which is now used by a causeway to connect the two sides. In its 1876âÂÂ77 session, the Outer House of the Court of Session decided that Dubh Loch was part of Fionn Loch, in an action brought by a fisherman who wanted to fish both lochs under the original fishing agreement without paying more. The decision was reversed by the Inner House of the court on appeal, before going to the House of Lords, where it was decided that both lochs were one. However, Dubh Loch is still marked as such on Ordnance Survey maps.