This book provides the most complete and updated picture of the research presently going on in the field of phosphazene materials all over the world. The large majority of scientists active in the phosphazene domain contributed to this book writing chapters on their own specific activity regarding these materials, also stressing future possible developments of this extremely interesting scientific and technologic area. Both cyclic and polymeric phosphazenes were described in this book, starting from the most representative and effective synthetic strategies used for their preparation, touching theoretical and spectroscopic research aspects for these materials, to conclude by reporting their possible practical use in several different application domains. This book provides the most complete and updated picture of the research presently going on in the field of phosphazene materials all over the world. The large majority of scientists active in the phosphazene domain contributed to this book writing chapters on their own specific activity regarding these materials, also stressing future possible developments of this extremely interesting scientific and technologic area. Both cyclic and polymeric phosphazenes were described in this book, starting from the most representative and effective synthetic strategies used for their preparation, touching theoretical and spectroscopic research aspects for these materials, to conclude by reporting their possible practical use in several different application domains.