Otto Hermann Krayer (22 October 1899 in Köndringen, Baden – 18 March 1982 in Tucson, Arizona) was a German-American physician, pharmacologist and university professor.
He was the only German scientist who refused on moral grounds to succeed a colleague who had been dismissed from his professorial chair by the National-Socialist government for anti-semitic reasons. Krayer voiced his opinion publicly and aggressively. The medical historian Udo Schagen entitled his historical analysis of Krayer: "Widerständiges Verhalten im Meer von Begeisterung, Opportunismus und Antisemitismus" or 'Resistant Behaviour in a Sea of Enthusiasm, Opportunism and Antisemitism'.[1]