Microcrystals of Th(HPO4)(2)center dot H2O were hydrothermally obtained from a Th(NO3)(4)-CO(NH2)(2)-H3PO3-H2O system (T= 180 degrees C). The structure [orthorhombic, Pbca, a = 9.1968(2) angstrom, b = 18.6382(2) angstrom, c = 8.7871(2) angstrom], unlike alpha-Zr(HPO4)(2)-H2O-type layered compounds, consists of a three-dimensional framework with PO4 tetrahedra coordinated to Th atoms. The water molecule is also coordinated to the Th atom and projected toward small channels running along the directions of the a and c axes. The ThO6O(w) environment could be described as a highly distorted pentagonal bipyramid.