Echu Tirmcharna mac Fergusso (died ca. 556) was a king of Connacht from the Uí Briúin branch of the Connachta. Genealogically he is mentioned as the great-great grandson of Dauí Tenga Uma (d. 500) a previous king. Prof. Byrne believes that the early Uí Briúin genealogies are fabricated however.^[1] His place in the king lists falls between the reign of Ailill Inbanda (d. 549) and of his son Áed mac Echach Tirmcharna (d. 575).^[2] The Annals of Tigernach simply mention him as king in 556 and his son's accession to the throne in 557.^[3]

A Poem on the Kings of Connaught describes him as Echu "dryflesh", the "choice man", and also as noble.