Arnold Otto Erich Brandenburg (31 July 1868 in Stralsund – 22 January 1946 in Leipzig) was a German historian. His main work Die Reichsgründung ("The Founding of the Reich", 2 vols. plus 1 vol. with documents) covers the origins of the modern German national movement and the founding of the Second Empire by Bismarck. The German historian Hans Herzfeld calls it "critical and reliable in its judgment" ("solide und kritisch zuverlässig im Urteil") and Herbert Helbig in Neue Deutsche Biographie "objective, deliberate and not without a critical attitude towards the problems of Bismarck's Empire" ("sachlich, kühl und nicht ohne kritische Einstellung zu der inneren Problematik des Bismarckreiches"). In 1933 Brandenburg signed the Vow of allegiance of the Professors of the German Universities and High-Schools to Adolf Hitler and the National Socialistic State.

Literary works (selection)