The RP Photonics Encyclopedia (formerly Encyclopedia of Laser Physics and Technology) is an encyclopedia of optics and optoelectronics, laser technology, optical fibers, nonlinear optics, optical communications, imaging science, optical metrology, spectroscopy and ultrashort pulse physics. It is available online as a free resource. An earlier version of the encyclopedia appeared as a two-volume book. As of March 2024, the online version of the encyclopedia contains 1043 articles.