The decision was widely expected after the deputy head of the FAS said last month the takeover would not give Gazprom a dominant position in the Russian oil sector.
The gas monopoly's $13.1 billion purchase of 72.7% of Sibneft, which is controlled by Chelsea football billionaire Roman Abramovich, will also be reviewed by competition authorities in the European Commission.
The EC said it was notified of the deal on 13 October and expects to complete its review by 22 November, although that deadline could be extended if it decides to seek more information on the deal.
