Dies irae (dē`ās ē`rā) [Lat.,=day of wrath], hymn of the Roman Catholic Church. A part of the Requiem Mass, it is a powerful description of the Judgment and a prayer to Jesus for mercy. Suggested in part by Zeph. 1.14–16, it was probably written by Thomas of Celano. In 16th-century polyphonic masses it was usually sung to the plain-song melody, but there are a few isolated examples of new music combined with the old melody in masses by minor composers. More recently, it has usually been supplied with new, and frequently intensely dramatic, music, notably by Mozart, Berlioz, and Verdi. It is no longer in general use in Roman Catholic funeral liturgy.