Geologically the Lough Neagh Basin is a depression, built from many tectonic events dating back as far as 400 million years ago.

[12][13][14][15] Towns and villages near the Lough include Craigavon, Antrim, Crumlin, Randalstown, Toomebridge, Ballyronan, Ballinderry, Moortown, Ardboe, Brockagh, Maghery, Lurgan and Magherafelt.

The counties are listed clockwise: The area of the lake is split between four local government districts of Northern Ireland, which are listed clockwise:[16] Lough Neagh is managed by Lough Neagh Partnership Ltd, a stakeholder group made up of elected representatives, land-owners, fishermen, sand traders and local community representatives.

Although the Lough is used for a variety of recreational and commercial activities, it is exposed and tends to get extremely rough very quickly in windy conditions.

The Lower Bann was also navigable to Coleraine and the Antrim coast, and the short Coalisland Canal provided a route for coal transportation.

Its members are highly trained and are a declared facility for the Maritime and Coastguard Agency which co-ordinates rescues on Lough Neagh.

[22] Nobel laureate Seamus Heaney produced a collection of poems A Lough Neagh Sequence celebrating the eel-fishermen's traditional techniques and the natural history of their catch.

[7] At the start of the Plantation of Ulster, the English attempted to rename the lake 'Lough Sydney' and 'Lough Chichester', in honour of the Lord Deputies, but these did not supplant the older name.

[27][28] According to the tale, the lake is named after Echaid (modern spelling: Eochaidh or Eachaidh), who was the son of Mairid (Mairidh), a king of Munster.

Dáithí Ó hÓgáin writes that the idea of a supernatural being creating the landscape with its own body is an ancient one common to many pre-Christian cultures.

[28] A Gaelic sept called the Uí Echach ("descendants of Echaid") dwelt in the area and it is likely their name comes from the cult of the god.

Another tale tells how the lake was formed when Ireland's legendary giant Fionn mac Cumhaill (Finn McCool) scooped up a chunk of earth and tossed it at a Scottish rival.

[30] Prior to the Tudor conquest of Ireland, the lough had been largely unclaimed by local Gaelic nobles, such as the O'Neill and O'Donnell dynasties.

During the reign of Elizabeth I, an Englishman, Sir Hugh Clotworthy, settled near Antrim as part of the Plantation of Ulster and was granted the office of "Captain of Lough Neagh" by the Dublin Castle administration, being paid a stipend in return for maintaining boats on the lough to enforce the Crown's authority.

He stated in the interview that "the sale is one that's borne out of an understanding that my ownership has always been very divisive and quite political and I always get blamed for things that are completely outside of my control.

"[35] In February 2024 concerns were raised at the sudden collapse in insect numbers on the Lough and the likely effects this will have on biodiversity in the area.

[36] Lough Neagh underwent catastrophic cyanobacteria or blue green algae bloom events in the summer of 2023 and 2024 which reached international news channels.

[37][38] This has led to numerous local community and environmental organization responses, such as a mock "wake" for the lake being held in protest and calls for drastic action to solve the problem.

The foremost contributory factor is the eutrophication of the lake with nutrients like phosphorus and nitrates which have provided suitable conditions for the algae to thrive.

[44][45] Key drivers of this eutrophication are increases in nitrates and phosphates in the lake which are generally attributed to runoff from agriculture in the form of animal slurry residue of chemical fertilizer in addition to human sewage.

Climate change has contributed to increasing summer temperatures of, and sunlight intensity on, the lake, creating more suitable conditions for rapid growth of harmful algal blooms.