Obninsk (Russian: О́бнинск) 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) from Kaluga. Population: 104,798 (2010 Census preliminary results).

The history of Obninsk began in 1945 when the First Research Institute Laboratory "V", which later became known as IPPE was founded. The city was built next to the plant in order to support it. Scientists, engineers, construction workers, teachers and other professionals moved to Obninsk from all over the Soviet Union. Town status was granted to Obninsk on June 24, 1956. The name of the city is taken from Obninskoye, the train station in Moscow-Bryansk railroad, built in Tsarist times.

Administratively, it is incorporated as the City of Obninsk—an administrative unit with the status equal to that of the districts.Municipally, the City of Obninsk is incorporated as Obninsk Urban Okrug.

According to the preliminary results of the 2010 Census, the population of the city was 104,798, down from 105,706 recorded in the 2002 Census, but up from 100,178 recorded in the 1989 Census.