Reductio ad Hitlerum, also argumentum ad Hitlerum, is a term coined by conservative philosopher Leo Strauss in 1951. According to Strauss, the Reductio ad Hitlerum is an informal fallacy that consists of trying to refute an opponent's view by comparing it to a view that would be held by Adolf Hitler or the Nazi Party.

According to Strauss, Reductio ad Hitlerum is a form of ad hominem or ad misericordiam, a fallacy of irrelevance, in which a conclusion is suggested based solely on something's or someone's origin rather than its current meaning. The suggested rationale is one of guilt by association. Its name is a variation on the term reductio ad absurdum.

Reductio ad Hitlerum is sometimes called playing the Nazi card, According to its critics and proponents, it is a tactic often used to derail arguments, because such comparisons tend to distract and anger the opponent.

In short, you lose.