The Vadakste () is a river in southern Latvia and northern Lithuania. It is a right tributary of the Venta River. The length is , of which over follow the LatviaâÂÂLithuania border. The catchment area is . It originates near the city Auce, Latvia. It flows first in a southwest, and then in a westerly direction. It begins to flow along the border between Latvia and Lithuania from the village of Vegeriai. It flows into Venta at from its mouth, in the village of Grieà ¾ÃÂ, northwest of Leckava.
The main tributaries: , , Agluona and Avëkne. The average river slope is 73 cm/km.