Polnaya (Russian: Полная, Ukrainian: Повна, romanized: Povna) is a river in the Rostov Oblast of Russia and the Luhansk Oblast of Ukraine, the left and largest tributary of Derkul. It is 79 kilometres (49 mi) long, and has a drainage basin of 2,390 square kilometres (920 sq mi).^[1] Its largest tributary is the Komyshna.