The Vadakste is a river located in southern Latvia and northern Lithuania. It serves as a right tributary of the Venta River, with a total length of approximately 82.2 km (51.1 mi). The river's catchment area covers 1,230 km² (470 sq mi).
The river originates near the city of Auce in Latvia and initially flows in a southwest direction before turning west. From the village of Vegeriai, it follows the border between Latvia and Lithuania for over 55 km (34 mi). It eventually flows into the Venta River at the village of Griežė, located 2 km (1.2 mi) northwest of Leckava.