TEORIANO. – Byzantine writer of the 12th century. The emperor Manuel Comnenus (1143–80) sent him twice, in 1170 and 1172, as his delegate to the Armenian patriarch Nerses II for negotiations concerning union, which remained fruitless, between the Byzantine and Armenian Churches. He also engaged in a religious dispute with the Jacobites. Documents of this activity are still extant. T. was conciliatory on the question of the azymes and maintained a firm and decisive position against Monophysitism.
BIBL.: PG 133, 113–298; A. Mai, Scriptorum veterum nova collectio, VI, I, Rome 1854, pp. 314–87; R. J. Loenertz, L'épître de Théorien le philosophe aux prêtres d'Oréiné, in Mémorial Louis Petit, Bucharest 1948, pp. 317–35.