Óengus of Tallaght was an Irish bishop and writer who lived during the early 9th century. A prominent member of the Culdee movement, he was a student of the reformer Máel Ruain at the monastery of Tallaght. He is most famous for composing the *Félire Óengusso*, a significant metrical martyrology written in the Irish vernacular. This poetic work contains a verse for every day of the year, documenting the feast days of various saints.