TANAIS was a River-God of Skythia, in North-Eastern Europe (the River Don, of modern-day Russia).

The Tanais River flowed through the eastern steppeland of Skythia, issuing into the Palus Maeotis (Sea of Azov), in the north-eastern corner of the Black Sea. The most important neighbouring rivers were the Borysthenes (Dnieper) in the west, and the Phasis of Kolkhis to the south.

Pseudo-Hyginus, Preface (trans. Grant) (Roman mythographer C2nd A.D.) :
"From Oceanus and Tethys [were born] the Oceanides . . . Of the same descent Rivers: Strymon, Nile, Euphrates, Tanais, Indus, Cephisus, Ismenus, Axenus, Achelous, Simoeis, Inachus, Alpheus, Thermodon, Scamandrus, Tigris, Maeandrus, Orontes."

Sources:

• Hyginus, Fabulae - Latin Mythography C2nd A.D.