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 von-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.