Loch Beinn a' Mheadhoin (Anglicised as Loch Benevian) is a freshwater loch in Inverness-shire, Scotland. It is one of several lochs in Glen Affric, a National Nature Reserve within Scotland's Caledonian Forest.

The loch is named after the mountain on its northwest shore, Beinn a' Mheadhoin, which translates from Scottish Gaelic to "Middle Mountain".

The Affric-Kintail Way runs along the loch's south shore.

In 2016, Scottish rewilding charity Trees for Life planted aspen along Loch Beinn a' Mheadhoin's shores to support the reintroduction of beavers.

The loch was partially expanded in the 1950s as part of the Affric-Beauly hydro-electric power scheme, drawing water from Loch Mullardoch to the north via a 5.5 km long tunnel. To this end, the loch has a small dam at its east end, and its water levels are artificially controlled.