The departure of Mack, 69, after less than a year on the board, comes after the United States imposed sanctions on Rosneft's head Igor Sechin over Russia's actions in Ukraine.
Rosneft said his decision to leave was not connected to the sanctions, adding that he is leaving for personal reasons.
A spokesman for Rosneft said that the decision on Mack's departure and his replacement would be taken at the annual general meeting scheduled for June 27.
The company also said that Artur Chilingarov, 74, has been proposed to replace Mack on the board. Chilingarov, a member of Russia's upper house of the parliament is best known as an explorer in the Arctic, a region seen as increasingly important for Rosneft's future as an oil and gas producer.
Mack is currently a senior adviser at KKR & Co and an independent non-executive director at Glencore.
He joined Rosneft's board last June after Rosneft bought Anglo-Russian oil firm TNK-BP for $55 billion from BP and the AAR consortium.
Six months later Rosneft announced it would buy the majority of the global physical oil trading operations of Morgan Stanley.
The Russian company has said that the deal with Morgan Stanley is intact and will be completed in the second half of this year.