As of Friday, the film had grossed $38.49 million.
The previous leader was "The Irony of Fate 2," which grossed $38.46 million, RIA Novosti reported
"Stalingrad," a love story set in 1942, is the country's first IMAX 3D product.
The film had a $30 million budget, which was partially funded by the state.
The movie received mediocre reviews in the media, RIA Novosti said, and it is the country's submission for foreign-language Oscar.
Oscar nominees will be announced in mid-January.