The book "Gradient-Index Optics" offers a comprehensive and detailed treatment of the fundamentals and applications of light propagation through inhomogeneous media. It is aimed at both students of physics and engineering as well as professionals, serving as a reference work. The authors explain the phenomena, components, and technologies used in GRIN optics. Additionally, the relationship to lenses, waveguides, optical connections, spatial solitons, and human perception is illustrated. The book analyzes the applications of GRIN components and hybrid structures in the fields of optical connections, optical sensing, and the Talbot effect.