The new quaternary group V thiophosphate K(4)VP(2)S(9) (tetrapotassium vanadium diphosphorus nonasulfide) was prepared by reacting a mixture of K(2)S(3), VP, P(4)S(3) and S. The crystal structure consists of discrete [VS(PS(4))(2)](4-) anions and K(+) cations. The V(4+) cation is in a fivefold coordination of S atoms which form a square-pyramidal environment. Each VS(5) group shares a common edge with two bidentate [PS(4)] tetrahedra, yielding the complete anion. The anions are stacked in the direction of the crystallographic b axis and are separated by the K(+) ions.