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.