GOI (ГОИ; Государственный оптический институт; Gosudarstvennyi opticheskii institut; State Optical Institute) is an optical research and development institute of the Soviet Union (and post-Soviet Russia). The Institute was set up in 1918. In 2005 it became GOI S.I. Vavilov in honour of the physicist Vavilov who was involved in the Insitute.
GOI designed the first versions of some photographic items that were later produced industrially. For example, GOI made the first versions of the Helios 40 and the Photosniper rifle-cameras.