(1) The ancient Greek name for the Rioni River, in what is now the Georgian SSR; the main river of Colchis. In the ancient world, the words “Phasis” and “Colchis” were often used synonymously.

(2) An ancient city and port on the Phasis River, founded in the sixth century B.C. by Greeks from Miletus. The city was the first point on a route that ran from the sea, along the navigable Phasis River, to the Surami Pass, and eventually to eastern Transcaucasia. In Roman and Byzantine times, Phasis was a fortress with a permanent garrison. In the 11th century it became the residence of the metropolitan of Lazica. Despite a reference by Strabo and information provided by travelers in the 18th and 19th centuries, the precise location of ancient Phasis has not been determined.