(Ἀμβρόσιος) ALEXANDRI'NUS, a nobleman and courtier (S. Epiph. ad v. Hacr. 64. [44] § 3) flourished A. D. 230. At first a Valentinian (Euseb. Hist. Eccl. 7.18) and Marcionist, he was won to the faith by Origen, whose constant fellow-student he became (Origen, Ep. ad African. vol. i. p. 29), and was ordained deacon. (S. Hier. Vir. Illustr. 56.) He plied Origen with questions, and urged him to write his Commentaries (ἐργοδιώκτης), supplying him with transcribers in abundance. He shone as a Confessor during the persecution of Julius Maximinus (Euseb. 6.18) A. D. 236, and died between A. D. 247 and 253. His letters to Origen (praised by St. Jerome) are lost; part of one exists ap. Origen, Lib. de Orat. 100.5. p. 208, A. B. (See Routh's Reliquiae Sacr. ii. p. 367.) Origen dedicated to him his and On Prayer.