AbstractSingle crystals of caesium gallium hydrogen phosphate, Cs2Ga(H2PO4)(HPO4)2· H3PO4· 0.5 H2O, were prepared by microwave‐induced heating (1 h) a mixture of CsGa(H2PO4)4and Cs2CO3in the excess of H3PO4. It crystallizes tetragonal, space group 141cd (N° 110 Int. Tab.) with Z = 16 and a = 2016.8(5), c = 1828.7(5) pm.The crystal structure was solved by using 3341 unique reflections Fo>4σ (Fo) with a final wR2 value of 0.1549 (SHELXL‐93).The main feature of the crystal structure are columns formed by PO4‐tetrahedra around the GaO6octahedra along the [001] direction. Cs+, H3PO4and H2O molecules connect the columns into framework. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), Charge Distribution (CHARDI) and the Madelung Part of Lattice Energy (MAPLE) are calculated for the title