Hermann Gerhardt Karl Oncken (16 November 1869 in Oldenburg, Germany – 28 December 1945 in Göttingen, Germany) was a German historian and political writer.
He was one of the most notable historians of pre-Nazi Germany.
He lectured at the universities of Chicago (1905), Giessen (1906), Heidelberg (1907–1923), Munich (1923–1928), and Berlin (1928–1935).
In 1935 he was forced to retire by the Nazi regime, which he opposed.
This article about a German historian is a stub.