Fiacha Finnfolaidh, son of Feradach Finnfechtnach, was a legendary High King of Ireland of the 1st century AD. He was overthrown by either Cairbre Cinnchait or Éllim, king of Ulster, in a revolt of the "subject peoples" against the Milesian nobility. His wife, Eithne, pregnant with his son Tuathal Teachtmhar, fled to Scotland.