The Stryama (Bulgarian: Стряма [ˈstrʲamɐ], known in Antiquity as Syrmus) is a river in southern Bulgaria, an important left tributary of the Maritsa. It originates in the Balkan Mountains. The river is 110 kilometres in length and is the sixth longest in the Maritsa drainage, following the Tundzha (390 km), the Arda (290 km), the Ergene (281 km), the Topolnitsa (155 km) and the Sazliyka (145 km). According to the Bulgarian linuist Yordan Zaimov, the etymology of the river derived from Thracian serm, meaning flow.