Lough Eske, Lake in County Donegal, Ireland.

Lough Eske is a freshwater lake located northeast of Donegal Town in County Donegal, with the Bluestack Mountains forming a natural backdrop on three sides. The lake receives water from four tributaries and drains through the River Eske into the wider river system.

The Ó Domhnaill (O'Donnell) chieftains held a castle and surrounding bawn on Island O'Donnell, near the southern shore of the lough, and often used the castle as a prison. Part of the bawn still stands on the island. After the Franciscan Friary in Donegal Town burned in September 1601, the friars fled and set up a new friary on the western shore, giving the townland the name 'The Friary'.

The name comes from the Irish Loch Iascaigh, 'Lake of the Fish'. After Donegal Town's Franciscan friary burned in September 1601 the friars moved to the western shore, leaving the townland name 'The Friary' in Killymard and the 'Friar's Walk' along the water. Roshin Island, in the southeast corner, is believed to have served the friars as a graveyard; graves are still visible there.

Fishing on the lake is regulated and, according to the French source, is possible only from boats rented on site; the season for spring salmon, sea trout and char runs from 1 March to 30 September. Walkers have unassigned paths on the south-western shore and reconstructed paths in Ardnamona Wood. The lake lies at 27 m altitude, northeast of Donegal Town.

In July 1998 the Irish Daily Star ran a story headlined 'Look out, it's Eskie', after staff and residents at Harvey's Point Hotel reported seeing an unidentified object moving about 300 metres from the shore at 2.30pm on Sunday, 28 June 1998. The tale gave the lake its own 'monster'.