The loss is compared to a net profit of 211.8 billion roubles in the same three months of 2019.
Russian companies, which carry debt denominated in foreign currency, have suffered losses due to the devaluation of the Russian rouble, which fell due to the pandemic.
Gazprom, which accounts for around 34% of the European gas market, reports earnings in roubles.
The gas producer said its net foreign currency-related loss stood at 464.3 billion roubles in the third quarter from a profit in the year-earlier period.
The Kremlin-controlled company also reported a decline in sales in Russia and Europe. Its average gas exporting price in the third quarter fell to $117.2 per 1,000 cubic metres from $169.8 in the same period last year.
Later on Monday, a company senior manager told a conference call for investors that Gazprom now sees its gas exports to Europe and Turkey in 2020 at around 171-172 billion cubic metres (bcm), up from a previous forecast of 170 bcm.
That’s still below its record-high of more than 200 bcm, exported in 2018, and around 199 bcm in 2019.
It also sees its average exporting gas prices to recover to $128-$130 per 1,000 cubic metres this year,
Gazprom said its revenue in the July-September quarter declined to 1.4 trillion roubles from 1.6 trillion roubles a year earlier.