Polyphosphazenes are a unique class of inorganic–organic hybrid polymers with a backbone composed of alternating phosphorus and nitrogen atoms. The ease with which the precursor prepolymer poly(dichlorophosphazene) can be modified has resulted in a versatile polymer system. The labile nature of the P−Cl bonds has allowed the substitution of chlorine atoms with groups like alkoxy‐, aryloxy, alkyl ether, fluoroalkoxy, amino acid/peptide esters, drug molecules, transition metal groups, and many more. Careful selection of the side groups offers efficient control of material properties such as bioactivity, crystallinity, solubility, and surface characteristics. Hence, these properties have led to the use of this exceptional class of polymers in a broad range of applications such as biomaterials for regenerative engineering and drug delivery, elastomers, solid membranes for gas/liquid separation, optical materials, flame retardants, and electrolytes for energy storage cells. This article gives an overview of the synthetic routes of polyphosphazene polymers and their composition–structure–properties relationships and highlights their applications in various fields.