A new imidooxonitridophosphate AlP6O3x(NH)3-3xN9 with x ≈ 0.33 was synthesized under high-pressure high-temperature conditions. The crystal structure determination of the microcrystalline product involved a combination of electron microscopy, synchrotron X-ray diffraction and solid-state NMR. In the solid there are discrete AlN6 octahedra that interconnect imidophosphate layers. The network topology is unprecedented but is related to other nitride structures.