KILLALA, DIOCESE OF. — It comprises parts of the Irish counties of Mayo and Sligo.
Out of a population of 56,980, it has 55,246 Catholics (census of 1936), distributed in 22 parishes, served by 55 diocesan priests; it has an ecclesiastical college (St. Muredach's College), 6 female religious communities, 108 primary schools, 5 secondary and 2 vocational schools. It is a suffragan of Tuam. The episcopal residence is in Ballina.
Its first bishop was St. Muredach, to whom St. Patrick entrusted the care of the church, called Cell Alaid, in the mid-5th century, from which the diocese derived its title of Alladensis. The patron saint of the diocese is the same St. Muredach (feast on 12 Aug.). Almost nothing is known of the series of bishops of K. until the end of the 12th century; in the Middle Ages the Franciscans had the famous convent of Moyne and later that of Rosserk, founded in 1460; the Dominicans had the abbey of Rathfran.