Otto Brass (21 December 1875 – 13 November 1950) was a German communist politician and anti-fascist activist.
In 1903, he became an administrator of the Remscheid workers' health insurance fund, then was appointed the business manager of the local socialist newspaper.
He was a founding member of the Communist Party of Germany (KPD), serving on its central committee, although he resigned from that in February 1921.
He was a leading member of the German Popular Front, and anti-Nazi group, in the 1930s, but was arrested in 1938 and spent the entirety of World War II in Brandenburg Prison.
After the war, he rejoined the KPD and lived in East Berlin, serving on the executive of the Free German Trade Union Federation.