Lough Erne (/lɒx ɜːrn/ LOKH URN, from Irish Loch Éirne) is the name of two connected lakes in County Fermanagh, Northern Ireland.

[5] Alternatively, John T. Koch suggests that Ériu was a mother goddess whose name comes from an Indo-European word stem meaning "fat, rich, fertile".

[6] Patricia Monaghan notes that "The drowning of a goddess in a river is common in Irish mythology and typically represents the dissolving of her divine power into the water, which then gives life to the land".

In folklore Partholón killed his wife's favourite hound, Saimer, in a fit of jealous rage, and the lake was named after it.

In the tale, Conn-eda goes on a quest to procure three golden apples, a black steed and a supernatural hound from a city underneath Lough Erne.

[11] The Menapii are the only known Celtic tribe specifically named on Ptolemy’s AD 150 map of Ireland, where they located their first colony, Menapia, on the Leinster coast circa 216 BC.

The Parliamentary Gazetteer of 1846 stated, "The islands are popularly fabled to be as numerous as the days of the year; but they have been more soberly estimated at 90 in the Upper Lake and 109 in the Lower".

Department for Infrastructure Rivers retains ownership of the bed and foreshore and manages water levels within the ranges specified in the Erne Drainage and Development Act (1950).

Water level control is undertaken in conjunction with the Electricity Supply Board (ESB) in the Republic of Ireland under the terms of an agreement made in 1950 when the River Erne was harnessed for hydroelectric power generation.

Water levels in Upper and Lower Lough Erne are managed by a control structures located at Portora in Enniskillen and by the hydro electric power station at Cliff between Belleek and Ballyshannon, in the Republic of Ireland.

During the summer period it is aimed to keep the water level at the down steam side of Portora, at or above, 150 ft. to avoid the need for the gates to be closed requiring the use of the navigation lock.

Rapid draw down of water levels in the Upper Lough is prevented by the restricted capacity of the inter-lough channel section.

This means that Rivers Agency must anticipate significant inflows by drawing down the loughs to ensure flood storage is available.

[22][23] A canal, the Shannon–Erne Waterway, runs between the upper end of the River Shannon and the River Erne, allowing boat movements from the Shannon estuary in southwest Ireland, through the western midlands of the country, across to the northwest and out to the Atlantic again (although the final section to the Atlantic side of Belleek is not navigable).

The section of the Ulster Canal connecting Lough Erne to Clones is being planned for navigation to be restored by Waterways Ireland.