[Ir., honourable champion (?), reticent nephew (?), Nár's man (?)].
Son of Lugaid Riab nDerg [Ir., red stripes], incestuously begotten with his mother Clothra, who had lain with her brothers Finn Emna to produce Lugaid; before this conception she visited the Otherworld and ate divine food. In another story he is slain when he attempts to kill Cúchulainn. A fortress at Howth, Dún Crimthann, was named for him; distinguish from another of the same name in Britain named for Crimthann Mór mac Fidaig.