An inorganic-organic hybrid crystal was synthesized by using polyoxomolybdate and hexadecylpyridinium surfactant. The unit cell was monoclinic having quite a long cell dimension (b = 75.0111(14)angstrom). The crystal structure was formed by alternative stacking of beta-octamolybdate bilayers and interdigitated hexadecylpyridinium bilayers with layered periodicity of 3.75 nm, which is the largest value for polyoxometalate-surfactant hybrid crystals.