Zmeï (Żmij, Zmey) is a legendary creature of the Slavic Mythologie, the enemy eternal of the celestial gods. One represents it like a snake or enormous a dragon spitting of the fire of his many heads (three, six, nine or twelve according to various versions). He fulfills an important function in the Slavic Cosmogonie. The legends tell that it was demolishes by Svarog during the creation of the world and used like swing-plow to trace the limits between the three spheres (Jav, VOR and Prav). Zmeï would then have been relegated to VOR, the kingdom of dead and the invisible one. According to other sources, Zmeï was a beneficial, protective creature water and seeds.

In Serbia, Croatia, Slovenia and with the Montenegro, it is known under the name of Zmaj (dragon), and in Poland the name of this god is Żmij (Vipère). The combat between Zmeï and Svarog can be to compare with the combat between Tiamat and Marduk in the Babylonian mythology.