Pattern-recognition systems, techniques, and applications using coherent optical systems are reviewed. Many optical pattern-recognition system architectures exist that include time-domain optical correlators and the optical joint transform correlators and refinements in the original optical matched spatial filter synthesis processor. Advanced optical pattern-recognition systems are also described such as hybrid optical/digital processors and diffraction-pattern sampling systems using specially shaped Fourier plane detector arrays. The optical space-variant pattern-recognition systems described are examples of the growing repertoire of operations now achievable in optical computers.