Lough Neagh is the largest freshwater lake in Ireland, and is also larger than any similar lake in Britain. Although extensive, the lake is quite shallow, being less than 15 metres deep. It is the central part of a sagging basin-like feature that owes its formation to subsidence over many millions of years.

The shoreline of Lough Neagh is divided among five of the six counties of Northern Ireland. The lough is famous for its eel fisheries. It has major potential as a recreational resource, and as a possible location for innovative new energy generation projects.