Organisation Consul (O.C.) was an ultra-nationalist, antisemitic and anticommunist terrorist organization active in Germany from 1920 to 1922. It was formed by members of the Marinebrigade Ehrhardt, a Freikorps unit which disbanded after the Kapp Putsch failed to overthrow the German Weimar Republic in March 1920. It was responsible for the assassinations of the Republic's Minister of Finance Matthias Erzberger on 26 August 1921 and German-Jewish Foreign Minister Walther Rathenau on 24 June 1922. In response to Rathenau's murder, the "Law for the Protection of the Republic" (Republikschutzgesetz) was enacted by the Reichstag, resulting in the banning of the O.C. on 21 July 1922. The O.C. assassinated at least 354 people.
The O.C. was created in 1920 by Captain Hermann Ehrhardt and some of his followers in the Marinebrigade Ehrhardt. They had been hiding out in Bavaria following the forced disbandment of Freikorps organizations after the Kapp Putsch of March 1920. His fighters had formed the Association of Former Ehrhardt Officers which then became the O.C. The founders used Freikorps contacts to recruit members in dozens of cities and small towns all over Germany. Eventually it came to have districts encompassing large swathes of the nation. They were particularly active in Berlin, where many of their crimes were committed. The O.C. had about 5,000 personnel.
The cultivation and dissemination of nationalist thinking; warfare against all anti-nationalists and internationalists; warfare against Jewry, Social Democracy and Leftist-radicalism; fomentation of internal unrest in order to attain the overthrow of the anti-nationalist Weimar constitution . . .
The organization of determined, nationalist-minded men . . . local shock troops for breaking up meetings of an anti-nationalist nature; maintenance of arms and the preservation of military ability; the education of youth in the use of arms.
Only those men who have determination, who obey unconditionally and who are without scruples . . . will be accepted. . . . The organization is a secret organization. "
At least 354 people were murdered for political reasons, between 1919 and 1922. Some notable victims are as follows:
- Hans Paasche - Retired Naval Officer, Pacifist. Shot in front of his children in his estate at Waldfrieden, 21 May 1920.
- Matthias Erzberger – Politician. Murdered by Heinrich Schultz and Heinrich Tillessen, 26 August 1921. Erzberger was targeted because he had signed the 1918 armistice.
- Karl Gareis – Politician in the Independent Social Democratic Party of Germany. Murdered.
- Philipp Scheidemann – Politician. Assaulted with prussic acid in the eyes, but escaped mostly unharmed.
- Marie Sandmayr – Servant who reported an illegal arms cache. Murdered by Schweighart and others.
- Walther Rathenau – Politician. Murdered by Ernst Werner Techow, Erwin Kern, and Hermann Fischer. June 24, 1922 
The Viking League eventually became related to the Nazi SA (storm troopers), but apparently by 1923, Hermann Göring writes that the Viking League had "declared war against the party and the SA". In 1934, Ehrhardt was on the list of people to be killed by the Nazi party during the Night of the Long Knives purge, but he escaped, and was later invited back to Nazi Germany. O.C. members went on to serve in the Nazi Schutzstaffel and were hailed as "heroes of the national resistance" under the Nazi regime.
- Waite, pp. 203, 213
- Waite, p. 215, quoting Friedrich Wilhelm Heinz, Sprengstoff, Berlin, 1930
- Selig 2012, p. 466.
- Waite, Vanguard of Nazism, 1969, p. 214, quoting, among other sources, Fried, Guilt of the Germany Army, 197, who in turn is quoting the Münchener Post, Dec 27, 1922
- Waite, p. 216
- Lange, p.250
- Waite, p. 217
- Waite, p. 218
- Waite, p. 222
- Waite, p. 219
- Waite, pp. 203–204
- Waite, p. 256
- Waite, pp. 279–280
- Waite, pp. 212–213
- Waite, p. 213
- Selig, Wolfram. "Organisation Consul". In Benz, Wolfgang (ed.). Handbuch des Antisemitismus. Judenfeindschaft in Geschichte und Gegenwart (in German). Berlin: De Gruyter. ISBN 978-3-11-027878-1.
- Waite, Robert G. L. (1969). Vanguard of Nazism The Free Corps Movement In Post-War Germany 1918-1923. New York:. W. W. Norton and Company.. 356 pages. ISBN 978-0-393-00181-5