This book is devoted to the formation and dynamics of localized structures (vortices, solitons) and of extended patterns (stripes, hexagons, tilted waves) in nonlinear optical resonators such as lasers, optical parametric oscillators, and the like. Theoretical analysis is performed by deriving order parameter equations, and also through numerical integration of microscopic models of the systems underinvestigation. Experimental observations, and possible technological implementations of transverse optical patterns are also discussed. A comparison with patterns found in other nonlinear systems, both optical systems and extended systems in general, is given.