The new thionyl phosphazene polymers, which contain recurring structural units corresponding to the following formula ##STR1## are prepared by ring-opening polymerization of cyclothionyl chlorophosphazene corresponding to the following formula ##STR2## at temperatures of 100.degree. to 300.degree. C. in the presence of an inert organic solvent and reaction of the polymer thus obtained, which corresponds to the following formula ##STR3## with salts corresponding to the following formulaM(R.sup.1 -R.sup.5)in the presence of an inert organic solvent at temperatures of 20.degree. to 200.degree. C.The new thionyl phosphazene polymers may be used for the production of thermoplastics, elastomers or thermosets.