Which pact of 1939 secretly divided Eastern Europe?

The Molotov–Ribbentrop Pact, officially the Treaty of Non-Aggression between Germany and the Union of Soviet Socialist Republics, was a non-aggression pact between Nazi Germany and the Soviet Union, with a secret protocol establishing Soviet and German spheres of influence across Eastern Europe. The pact was signed in Moscow on 24 August 1939 by Soviet Foreign Minister Vyacheslav Molotov and German Foreign Minister Joachim von Ribbentrop.