Otto Bauer (1881 - July 4, 1938) was an Austrian Social Democrat who is considered one of the leading ideological thinkers of the Austro-Marxist movement.

Having studied at the University of Vienna, he finished is PhD in Law in 1906 and published his first book, Die Sozialdemokratie und die Nationalitätenfrage, in 1907. Although he was politically active during his studies, his gradual rise in the Austrian Social Democratic Party began after he had finished his PhD. He was able to establish himself as a likely heir to the throne of Viktor Adler.

Otto Bauer was a P.O.W. in World War I and returned from Russia to Austria in 1917. After Viktor Adler's death, Otto Bauer was appointed the first Minister of Foreign Affairs of the first Austrian Republic in November 1918. As a Minister of Foreign Affairs, Bauer's main goal was to annex Austria to the Weimar Republic, i.e. to make the Anschluss possible. Having failed at his main political goal, Bauer resigned from his post in July 1919.

Otto Bauer was forced into exile in 1934 after the Christian Democratic leaders put an end to an attempt of the Austrian Social Democrats to take over the country. Otto Bauer continued to organize the Austrian Social Democrat's resistance first from Brno and later from Paris, France. He continued his literary and theoretical work until his very last breath. He died in Paris, France, on 4th of July 1938, aged 57, merely four months after Austria had become part of Hitler's Reich.