Thermotropic ionic liquid crystals of polyoxometalate (POM)-based ionic liquids (POM-based ILs), which are formed by a POM, K7PW11O39, and cationic surfactants, tetra-n-alkylammonium bromide ((CnH(2n+1))(4)N+Br-, n = 6 and 7), are first proposed. As a model system, the cubic phase structure of a POM-based IL, {(C7H15)(4)N+}(7)PW11O39, was determined to form in a wide range of temperatures, exhibiting good thermostability, excellent mechanical strength, and high viscosity. Furthermore, the lyotropic ionic liquid crystals formed by {(C7H15)(4)N+}(7)PW11O39 in solvents such as chloroform or toluene still maintained a cubic structure. These cubic ionic liquid crystals (CILCs) were used as anticorrosion coatings both in acidic and neutral environments. The electrochemical measurements of Cu and Fe surfaces coated by CILCs showed an excellent ability of anticorrosion, indicating that the metals can be perfectly protected by the CILC coatings with high resistance and low capacitance. We assume that the CILCs may serve as barriers to stop oxygen diffusing to metals and interrupt the electron tunnels between the metal surfaces and the electrolyte solutions. Such environmentally friendly CILCs of POMs-based ILs are convenient for coating and removal, being vital to versatile industrial and academic applications.