Colchis , ancient country on the eastern shore of the Black Sea and in the Caucasus region. Centered about the fertile valley of the Phasis River (the modern Rion), Colchis corresponds to the present-day region of Mingrelia in Georgia. In Greek legend it was the home of Aeëtes and Medea, the land where the Golden Fleece was sought by Jason and the Argonauts. Greek trading posts were established in Colchis, but the land remained independent until conquered (c.100 B.C.) and held briefly by Mithradates VI of Pontus. After the time of Trajan to the end of the Roman Empire, Rome exerted considerable influence on the region.