archbishop of Milan (398-400), was a friend and teacher of Ambrose, who wrote to him four epistles (comp. Migne, 16, 874). Augustine dedicated to Simplicianus his De Diversis Quoestionibus, and mentions him very often. Virgilius of Trent addressed to him his De Martyrio S. Sisinnii et Socinorum (Migne, vol. 13), and Ennodius of Pavia wrote an epigram in his honor. See Gennadius, De Viris Illust. p. 27. (B.P.)