A new phosphate, K2(VO)3(HPO4)4, has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility. The title compound crystallizes in the monoclinic space group P2 c with a = 10.756(1), b = 9.147(3), c = 8.662(1) Å, β = 112.842(9)°, Z = 2, and R = 0.034. The structure is built from infinite chains of vertex-sharing vanadium oxide octahedra and HPO4 groups with the potassium cations located in sites within tunnels and cages in the structure. These infinite chains have alternating short and long VO bonds. Each phosphate tetrahedron shares vertices with three octahedra, but two of these belong to the same infinite chain.