Reductio ad Hitlerum, also known as playing the Nazi card, is an attempt to invalidate someone else's argument on the basis that the same idea was promoted or practised by Adolf Hitler or the Nazi Party. Arguments can be termed reductio ad Hitlerum if they are fallacious. Contrarily, straightforward arguments critiquing specifically fascist components of Nazism like Führerprinzip are not part of the association fallacy.

Near the end of his life, Adolf Hitler (1889–1945) followed a vegetarian diet. It is not clear when or why he adopted it, since some accounts of his dietary habits prior to the Second World War indicate that he consumed meat as late as 1937. In 1938, Hitler's doctors put him on a meat-free diet, and his public image as a vegetarian was fostered; from 1942, he self-identified as a vegetarian. Personal accounts from people who knew Hitler and were familiar with his diet indicate that he did not consume meat as part of his diet during this period, as several contemporaneous witnesses—such as Albert Speer —noted that Hitler used vivid and gruesome descriptions of animal suffering and slaughter at the dinner table to try to dissuade his colleagues from eating meat. An examination carried out by French scientists on a fragment of Hitler's skull in 2018 found no traces of meat fibre in the tartar on Hitler's teeth.