Kyrie Eleeison (Κύριε ἐλέησον, Lord have mercy [upon eus]), the well-known form of earnest and pathetic penitential appeal of the Scriptures, of frequent occurrence in the services of the early Church, and in the liturgical formulae of the Eastern and Western churches, and since the Reformation retained even in many Protestant churches.
Eastern Church. — Most frequently it was used in the opening portions of the ancient liturgies. In that of St. Mark we find three long prayers, each preceded by the threefold repetition of the Kyrie. In St. Chrysostom's the deacon offers ten petitions, and each is followed by the answering Kyrie of the choir. In the Apostolic Constitutions (lib. 8:can. 6), when the catechumens are about to pray, all the faithful add for them this supplication (comp. Neale, Primitive Lit. p. 88).
Western Church. — In the West the Kyrie Eleeison and Christe Eleeison, termed by St. Benedict "lesser" or " minor litany," it is generally supposed were introduced by pope Sylvester I (314-335), and formed a part of the Preces Feriales of the " Salisbury Portiforium," as they do now of the daily offices of prayer of the Church of Rome, England, and the Protestant Episcopal Church. In the Lutheran and many other evangelical liturgies the Kyrie Eleeison is retained. See Palmer, Oriq. Lit. i, 122; Siegel, Christlich- Kirchliche Alterthiimer, 3:237; Riddle, Christian Antiquities, p. 381; Walcott, Sacred Archceol. s.v.; Proctor, Common Prayer (see Index); Blunt, Dict. Doct, and Hist. Theol. s.v. (J. H. W.)