ILARIUS of Arles. – A monk of Lérins, semi-Pelagian, d. 444. Metropolitan of Arles, he came into conflict with Pope Leo the Great (L. Duchesne, Fastes épiscopaux de l'ancienne Gaule, I, 2nd ed., Paris 1907, pp. 112-29).
He wrote a Vita s. Honorati decessoris sui (Gennadius, De vir. ill., 60; PL 50, 1249-72). The life of I. (PL 50, 1249-46) mentions other writings of his: Homiliae in totius anni festivitatibus expeditae, Symboli expositio ambienta, Epistolarum vero tantus numerus, versus etiam fontis ardentis. Little of this has survived.
Bibl.: The remains of I.’s writings in the edition by the Ballerini brothers of the Works of Leo the Great, II, Venice 1753-57, pp. 305-92; cf. A. Ries, Anthologia latina, 2nd ed., Leipzig 1906, no. 487. On his life: B. Kolon, Die vita s. Hilarii Arelat., Paderborn 1925; Bardenhewer, IV, pp. 571 ff.