Dub-dá-leithe (d. 1064), abbot of Armagh, belonged to the Clann Sínaig (who had controlled the abbacy for many generations), and was son of Máel-Muire (qv) (d. 1020) and a grandson of Eochaid grandson of Flann/Flannacán; he also had some consanguinity with the Cenél nÉogain, as his genealogy shows. He was fer léigind of the monastic school of Armagh (1046–9) and abbot (1049–60), having been preceded in that position by his brother Amalgaid (qv) and by his grandfather Eochaid. Dub-dá-leithe's abbacy was marred by the murder in 1052 of the vice-abbot (secnab) Gilla-Pátraic son of Domnall, in which he was probably implicated. His later rival for the abbacy, Cummascach grandson of Erodán, seems to have belonged to the same sept as Gilla-Pátraic – the Uí Bresail – and may have been his brother, which would certainly explain the continuing rivalry between Dub-dá-leithe and Cummascach for the control of the position. This eventually led to Dub-dá-leithe's removal from the abbacy by Cummascach in 1060.
Dub-dá-leithe died in 1064, after which his nephew Máel-Brigte was installed as abbot, so that the tradition of Clann Sínaig control of the abbacy of Armagh continued. He was the author/compiler of the ‘Book of Dub-dá-leithe', a collection of annalistic, saga and poetry material, which was a source in the compilation of the Annals of Ulster and apparently survived till the seventeenth century.