The crystal structure of the compound terbium pentaphosphate has been determined from three dimensional intensities measured with an automatic Phillips PW-1100 single crystal diffractometer. The atrnctnre was solved by heavy-atom method.It has a monoclinic unit cell with a=8.721(3),b=8.877(2),c=12.911(1) Å,β=90.52(2)°and Z=4. The space group is C³_2h-P2₁/c. The poaitional and acale parameters with anisotropic temperature factors for the atoms were refined by fixllmatrix and block-diagonal least squaraa calculations to a final R=0.075 and R_W=0.079. The result of atrnctural analysis establishes that the structure is built up with discrete anionic ribbons linked by the nations in a complex way. The coordination of the ration by oxygen atoms is eight-fold with the geometry of a slightly distorted square antiprigm. Tb-Tb distance is 5.904Å.