|Location||Kyiv (to the north), Kyiv Oblast, Ukraine|
|Primary inflows||Dnieper River|
|Primary outflows||Dnieper River|
|Basin countries||Russia, Belarus, Ukraine|
|Max. length||110 km|
|Max. width||12 km|
|Surface area||922 km²|
|Max. depth||8 m|
|Water volume||3.7 km³|
|Surface elevation||99 m|
The Kyiv Reservoir (Ukrainian: Київське водосховище, Kyyivs’ke vodoskhovyshche), locally the Kyiv Sea, is a large water reservoir located on the Dnieper River in Ukraine. Named after the city of Kyiv, which lies to the south, it covers a total area of 922 square kilometres within the Kyiv Oblast. The reservoir was formed in 1960-1966, as a result of the Kiev Hydroelectric Power Plant dam being built at Vyshhorod. The reservoir is mainly used for hydroelectricity generation, industrial and public consumption, and irrigation.
The reservoir is 110 km in length, 12 km in width, has a depth of four to eight meters, a volume of 3.7 km³, and a usable volume of 1.2 km³. The reservoir, together with the Kakhovka Reservoir, the Dnieper Reservoir, the Dniprodzerzhynsk Reservoir, the Kremenchuk Reservoir, and the Kaniv Reservoir, has created a deep-water route on the river. However, the construction has also contributed to significant environmental problems such as the diminished flow velocity which reduces water oxygenation, and has a negative result on the balance of aquatic life forms. Also, during its construction some nearby villages were flooded. One of these was Teremtsi, where the residents of the village persuaded Soviet authorities to let them stay, only to be evacuated later in 1986.
Like all Dnieper reservoirs, Kyiv reservoir poses potential threat of tremendous flooding if its dam is destroyed. Moreover, it contains additional major threat - after the Chernobyl Nuclear Disaster in 1986, radionuclides washed away by rains badly contaminated the bottom silt of the reservoir. During the years following the disaster, there were suggestions to drain the reservoir because it was too shallow. It appeared that, if done, this could have created the threat of the tremendous amounts of radioactive dust travelling by wind, lethally affecting Europe.
A similar threat is permanently discussed regarding the potential destruction of the reservoir's dam (as a result of natural accident or terrorist damage). But the authorities continue to dismiss such dangers as unreal, claiming to be in full control of the dam's safety. However, serious concerns were raised in 2005, when a fake terrorist alert was made.