HEPHÆSTIO, a grammarian of Alexandria, in Egypt, who lived A. D. 150, and is supposed to have been one of the preceptors of Ælius Verus, mentioned by Julius Capitolinus in his life of that emperor. (Vit. Veri, c. 2.) Suidas states that he was a voluminous writer, though chiefly on grammar and metres; but, of all his works, nothing has been preserved except an Elementary Treatise on Metres. (Εγχειρίδιον περὶ μέτρων καὶ ποιημάτων.) Though this work is by no means complete, nor always correct, still it is valuable as being the only one on that subject which has reached us. It has been illustrated by numerous scholia; and there is an introduction to it (πρόλογος), ascribed to the celebrated Longinus, which was first published by Hudson in the preface to his edition of the work (περὶ ὑπόνοις), Oxford, 1710. The principal editions of this work of Hephæstio are, Florent. ap. Junt. 1526; Par. ap. Turnebum, with scholia, 1553; Trajecti ad Rhenum, ap. Pauw, 1726; but the best is by Gaisford, Oxford, 1810.