Lough Mourne is located about 9 kilometres (6 mi) southwest of Ballybofey, near the N15 road.

[5] The Mourne Beg River flows out of the southern end of the lough,[2] while the Burn Daurnett flows out of the north-eastern end of the lough.

The Red Burn (also known as the Sruhanderg) flows into the western side of the lough.

Fish species in Lough Mourne include roach, pike, brown trout and the critically endangered European eel.

[3] The southwestern shore of Lough Mourne forms part of the Croaghonagh Bog Special Area of Conservation.