Introduction to Solid State Ionics: Phenomenology and Applications presents a pedagogical, graduate-level treatment of the science and technology of superionic conductors, also known as fast ion conductors or solid electrolytes. Suitable for physics, materials science, and engineering researchers and students, the text emphasizes basic physics and chemistry as well as applications of electrochemical energy materials. The book focuses on fundamental phenomenological aspects, including crystal structure, phonon dispersion, electronic band structure, defects, disorder, nonstoichiometry, non-equilibrium thermodynamics, phase transitions, and statistical mechanics of iono-electron transport. It explains how the design, synthesis, and characterization of materials aid in optimizing diffusion coefficients and ionic conductivities. The author also describes important applications of solid state ionics, including solid state batteries, fuel cells, and electrochemical sensors.