Lough Fern (Irish: Loch Fearna)[4] is a freshwater lake in the northwest of Ireland.

It is located in north County Donegal near the town of Milford.

The lake drains eastwards into the continuation of the Leannan, which in turn enters Lough Swilly at Rathmelton.

[2][3][5] Fish species in Lough Fern include brown trout, salmon, three-spined stickleback, perch and the critically endangered European eel.

[6] Lough Fern is part of the Leannan River Special Area of Conservation.