Kosmos 27 (Russian: Космос 27 meaning Cosmos 27), also known as Zond 3MV-1 No.3 was a space mission intended as a Venus flyby. The spacecraft was launched by a Molniya-M carrier rocket, however an upper stage malfunction resulted in the spacecraft failing to leave low Earth orbit.
Beginning in 1962, the name Kosmos was given to Soviet spacecraft which remained in Earth orbit, regardless of whether that was their intended final destination. The designation of this mission as an intended planetary probe is based on evidence from Soviet and non-Soviet sources and historical documents. Typically Soviet planetary missions were initially put into an Earth parking orbit as a launch platform with a rocket engine and attached probe. The probes were then launched toward their targets with an engine burn with a duration of roughly 4 minutes. If the engine misfired or the burn was not completed, the probes would be left in Earth orbit and given a Kosmos designation.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Manned flights are indicated in bold text. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in brackets.