Virtually no modern optical system could operate without optical coatings. Much of any optical system consists of a series of coated and shaped surfaces. The shape determines the power of the surface but it is the coating that determines the specular properties, the amount of light transmitted or reflected, the phase change, the emittance, the color, the polarization, the retardation, including even the mechanical properties. Optical coatings consist of assemblies of thin films of materials where interference properties combine with the intrinsic properties of the materials to yield the desired optical performance. They act to reduce the reflectance losses of lenses, increase the reflectance of mirrors, reduce glare and electromagnetic emission from display systems, improve the thermal insulation of buildings, protect eyes from laser radiation, analyze gases, act as anticounterfeiting devices on banknotes, multiplex or demultiplex communication signals, separate or combine color channels in display projectors, and these are just a few of their roles. This course emphasizes understanding and takes students from fundamentals to techniques for design and manufacture.