A potassium silicophosphate, K₂SiP₄O₁₃, has been synthesized in molten polyphosphoric acid. It crystalizes in the triclinic space group P  (No. 2) with a = 4.8327(10), b = 7.7403(15), c = 14.485(3) Å, a = 82.29(3)°, b = 83.31(3)°, g = 81.95°, V = 529.02(19) ų, Z = 2. The crystallographic structure features 2D layers of [SiP₄O₁₃]_¥ in the ab plane with counter cations K⁺ residing among the layers, and the anionic framework of [SiP₄O₁₃]_¥ is composed of six-fold coordinated Si atoms and tetraphosphate anions by sharing vertex O atoms. The title compound was characterized by powder X-ray diffraction, IR and Raman spectroscopies, UV-vis diffuse reflectance spectroscopy, thermogravimetry and differential scanning calorimetry.