Varbitsa (Bulgarian: Върбица) is a river in the Eastern Rhodope mountains in Bulgaria.The Varbitsa river, a tributary to the Arda, the main river of the Rhodope Mountains, runs through 8 municipalities, 6 of them within the region of Kardjali and 2 in the region of Smolyan. It is the lifeline of the area, with industrial, drinking and irrigation water coming out, and refuse, raw sewage and industrial waste going in.