Obninsk Nuclear Power Plant was built in the "Science City" of Obninsk, Kaluga Oblast, about 110 km (68 mi) southwest of Moscow, Soviet Union. Connected to the power grid in June 1954, Obninsk was the first grid-connected nuclear power plant in the world, i.e. the first nuclear reactor that produced electricity industrially, albeit at small scale. It was located at the Institute of Physics and Power Engineering. The plant is also known as APS-1 Obninsk. It remained in operation between 1954 and 2002. Its production of electricity for the grid ceased in 2002; thereafter it functioned as a research and isotope production plant only.

Obninsk is a city in Kaluga Oblast, Russia, located on the bank of the Protva River 100 kilometers (62 mi) southwest of Moscow and 80 kilometers (50 mi) northeast of Kaluga. Its population is 125,376 at the 2021 census.