Thorium (Th 4+) and cerium (Ce 4+) phosphonates have been synthesized by the sol–gel method using various phosphonic acids and analyzed using elemental and CHN analysis, spectral analysis (Fourier transform infrared spectroscopy and X-ray diffraction), thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The proton transport study was performed by measuring proton conductance at different temperatures using an impedance analyzer. The Grotthuss mechanism of the proton conduction has been discussed thoroughly on the basis of results obtained from the impedance measurement; the specific proton conduction (σ) and activation energy ( E a) have been evaluated and compared with the reported proton-conducting system having similar phosphonate moieties.