Iāson or Iāso (e. g. Mel. 1, 19, 5), onis, m., = Ἰάσων. Jason, a famous Grecian hero, son of Aeson, king of Thessaly, the leader of the Argonauts, a sharer in the Calydonian boar-hunt, the husband of Medea, and afterwards of Creūsa, Cic. Tusc. 4, 32, 69; Ov. M. 7, 5 sq.; 8, 301; 348; Val. Fl. et saep.; Hyg. F. 12, 14; 16: quo jam mercator Iason clausus et armatis obstat casa candida nautis, i. e. when the fresco in the portico of Agrippa, representing Jason and his sailors, is hidden by the white canvas tents of the dealers at the fancy fair, Juv. 6, 153 sq.

—Also, the name of a poem by Varro Atacinus, Prop. 2, 34 (3, 32), 85.

— Derivv. Iāsonius, a, um, adj., of or belonging to Jason: carina, i. e. the ship Argo, Prop. 2, 24 (3, 19), 45: remige, i. e. Argonautic, Ov. P. 3, 1, 1.

— Iāsonides, ae, m., a male descendant of Jason: juvenes, i. e. Thoas and Euneus, sons of Jason, Stat. Th. 6, 340.

— A ruler of Pherae, in Thessaly, Cic. Off. 1, 30, 108; id. N. D. 3, 28, 70; Val. Max. 9, 10; Nep. Timoth. 4, 2.