LÉ Eithne (P31) is an Eithne-class ship in the Irish Naval Service. The ship is named after Eithne, a tragic heroine and the daughter of the one-eyed Fomorian King, Balor in an early Irish romantic tale. Eithne was originally built as a long range fisheries patrol vessel, intended to be at sea for up to 19 days. It was originally planned to order four vessels of this class, but budget restrictions prevented this. Eithne is currently the flagship of the Irish Naval Service.