|Mission type||ASAT target|
|Launch mass||650 kilograms (1,430 lb)|
|Start of mission|
|Launch date||8 July 1976, 21:08UTC|
|Launch site||Plesetsk 132/1|
|Perigee altitude||915 kilometres (569 mi)|
|Apogee altitude||2,053 kilometres (1,276 mi)|
Kosmos 839 (Russian: Космос 839 meaning Cosmos 839) was a satellite which was used as a target for tests of anti-satellite weapons. It was launched by the Soviet Union in 1976 as part of the Dnepropetrovsk Sputnik programme, and used as a target for Kosmos 843 as part of the Istrebitel Sputnikov programme.
Kosmos 839 was placed into a low Earth orbit with a perigee of 915 kilometres (569 mi), an apogee of 2,053 kilometres (1,276 mi), 65.9 degrees of inclination, and an orbital period of 115.6 minutes. It was successfully intercepted by Kosmos 843 on 21 July. As of 2009, debris is still in orbit.
Kosmos 839 was the third of ten Lira satellites to be launched, of which all but the first were successful. Lira was derived from the earlier DS-P1-M satellite, which it replaced.