Abstract Li 2WO 4(IV), the densest phase among four polymorphs, crystallizes with monoclinic symmetry, C2 c , a = 9.753(1) Å, b = 5.954(1)Å, c = 4.994(1)Å, β = 90.58(2)°, Z = 4, D calc = 6.00 g cm −3. The structure was determined by 1765 counter-measured independent reflections with a single crystal synthesized at 40 kbar and 850°C, and refined to R = 0.067 by the full-matrix least-squares method. It is based on a hexagonal closest arrangement of oxygen atoms and is structurally closely related to the wolframite-type structure. Both the tungsten and the lithium atoms are in octahedral sites. The structure consists of four octahedral layers parallel to (100). The first and the third layers are filled by lithium atoms, resulting in LiO 6 octahedral sheets, while the second and the fourth contain zigzag chains of WO 6 octahedra observed in the wolframite structure.