Otto Johann Maximilian Straßer (10 September 1897 – 27 August 1974), often Strasser in English, was a German politician and an early member of the NSDAP.
Otto Straßer was the brother of Gregor Straßer. The Straßer brothers supported relatively left-wing views within the NSDAP, such as the nationalization of the economy, causing conflicts with Adolf Hitler. He was expelled from the NSDAP by Hitler in 1930. Following his expulsion, he set up his own party, the Black Front, composed of like-minded former NSDAP members, in an unsuccessful attempt to split the NSDAP. He left Germany in 1933 as Hitler rose to power.
Straßer was permitted to return to West Germany in 1955, after years of being denied entry. He attempted to create a new "nationalist and socialist"-oriented party in 1956, the German Social Union, which was dissolved in 1962.