Shadowy king of pre-Patrician Ireland, third in line before the Lóegaire who disputes with the evangelist. He is described as being of Munster stock and unrelated to other kings at Tara; he would have just preceded Niall Noígiallach [Ir., of the Nine Hostages]. Although his name appears in many Irish records, Crimthann's historicity is, in the words of T. F. O'Rahilly, ‘unworthy of credence’. His reputed sister Mongfhind is clearly supernatural. He perishes through the sorcery of another supernatural woman. The cannibalistic Eithne Uathach [Horrible, Dreadful] is sometimes described as his daughter. The fortress built by the Irish near the River Dee in Britain, Dind Traduí, sometimes carries the name Dún Crimthainn in allusion to Crimthann Mór mac Fidaig. This should be distinguished from another fortress named Dun Crimthainn at Howth named for Crimthann Nia Náir. See also Aided Chrimthaind Maic Fhidaig [The Death of Crimthann mac Fidach], ed. Whitley Stokes, Revue Celtique, 24 (1903), 172–89.