Baron Roman Nikolai Maximilian von Ungern-Sternberg (December 29, 1885 ??September 15, 1921) was a Baltic Swedish-Russian Yesaul (Cossack Captain), a Russian hero of World War I and Lieutenant-general at the time of civil war in Russia and Mongolia, who 'liberated' Mongolia from Chinese rule in February - March 1921. In June he invaded Southern Siberia trying to raise an anti-communist rebellion, but was defeated by the Red Army in August 1921.

An independent and brutal warlord in pursuit of pan-monarchist goals in Mongolia and territories east of Lake Baikal during the Russian Civil War that followed the Bolshevik Revolution of 1917, Ungern-Sternberg's goals included restoring the Russian monarchy under Michael Alexandrovich Romanov and the Great Mongol Empire, with Outer Mongolia under Bogd Khan as part of it. His opponents were mainly Communists.

Ungern-Sternberg often persecuted those who were helping his foes: all Reds and especially Jews. Following his Asiatic Cavalry Division collapse in Mongolia, Ungern-Sternberg was left by his Russian officers and taken prisoner by the Bolshevik's Red Army. He was tried and executed for his counter-revolutionary involvement in Novosibirsk.