In the system Na2O-Ta2O5-P2O5 a notable glass formation could be found in the region of composition Na4TaP3O12. The sodium tantalo-phosphate glasses that have been investigated are characterized by an extraordinary Na+ mobility in comparison with other glassy oxide electrolytes with about 1.5 X 10(22) Na+/cm3, verified by impedance spectroscopy and interpreted by NASICON-like oxo-coordination polyhedrons of the glass network.