Black Pig's Dyke

The Black Pig's Dyke (Irish: Claí na Muice Duibhe) or Worm's Ditch (Irish: Claí na Péiste) is a series of discontinuous linear earthworks in southwest Ulster and northeast Connacht, Ireland. Remnants can be found in north County Leitrim, north County Longford, County Cavan, County Monaghan and County Fermanagh (see the map below). Sometimes, the Dorsey enclosure in County Armagh and the Dane's Cast in County Down are considered to be part of the dyke.

Similar earthworks can be found throughout Ireland, although the Black Pig's Dyke is the best known. A notable example is the Claidh Dubh ("black ditch"), anglicised Clyduff or Cleeduff, in eastern County Cork. It has three sections, the longest of which runs north–south for 24 kilometres (15 mi) from the Ballyhoura Hills to the Nagle Mountains.