This text deals primarily with the optics of refracting and reflecting planar surfaces in the form of prismatic refracting and reflecting components, and the design, analysis, and applications of these components. Optical prisms consist of multiple planar surfaces, constructed to a specified geometry and formed from optical glass or plastic. The surfaces may have thin-film coatings that contribute to their functionality. Optical prismatic elements can be classified into two general types: those that are used in imaging systems, such as binoculars or projectors, and those used in nonimaging systems, such as spectrometers, illuminators, and solar concentrators. In addition to well-known prism systems, new applications of prisms are being introduced in the fields of electro-optics, metrology, prismatic films and arrays, projection displays, and others.