Otto Johann Maximilian Strasser (September 10, 1897 - August 27, 1974) was a German politician and left-wing member of the Nazi party who rejected Adolf Hitler's ideas and formed his own faction, along with his brother, Gregor Strasser.

Born in Bavaria, he took part in World War I and returned to Germany in 1919 where he served in the Freikorps that put down the Munich Soviet and also joined the Social Democratic Party. In 1920 he participated in the opposition to the Kapp Putsch. However, he grew increasingly alienated with the party's stand, particularly when it put down a worker's uprising in the Ruhr, and he left the party later that year. In 1925 he joined the Nazi Party, which his brother had been a member of for several years, and worked for its newspaper, Arbeiter Zeitung, as a journalist, ultimately taking it over with his brother. He took the socialist element in the party's programme seriously enough to lead a left-wing faction of the party in northern Germany with his brother Gregor and Joseph Goebbels. His faction advocated support for strikes, nationalisation of banks and industry, and closer ties with the Soviet Union. These policies were opposed by Hitler, and the faction was defeated at the Bamburg Conference (1926), with Joseph Goebbels joining Hitler. Humiliated, he nonetheless, along with his brother Gregor, continued as a leading Left Nazi until expelled by Hitler in 1930.

Following his expulsion, he set up his own party, The Black Front, composed of radical ex-Nazis, in an attempt to split the Nazi Party. His party proved unable to counter Hitler's rise to power in 1933, and Strasser spent the years of the Third Reich in exile. The Nazi Left itself was annihilated during the Night of the Long Knives in 1934 (in which his brother perished), leaving Hitler as undisputed party leader.

Strasser settled first in Switzerland in 1938 and then, in 1940, he went to Bermuda by way of Portugal, leaving a wife and two children behind in Switzerland. In 1941, he emigrated to Canada, settling for a time in Montreal. In 1942, he settled in Paradise, Nova Scotia, where he lived for more than a decade in a rented apartment above a general store under the pseudonym "Adolph Schmidt." He does not seem to have ever attempted to reestablish contact with his family or bring them over to live with him after the war.