Godwin's law, short for Godwin's law of Nazi analogies, is an Internet adage asserting: "As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1."

Nazi analogies or Nazi comparisons are any comparisons or parallels which are related to Nazism or Nazi Germany, which often reference Adolf Hitler, Joseph Goebbels, the SS, or the Holocaust. Despite criticism, such comparisons have been employed for a wide variety of reasons since Hitler's rise to power. Some Nazi comparisons are logical fallacies, such as reductio ad Hitlerum. Godwin's law asserts that a Nazi analogy is increasingly likely the longer an internet discussion continues; Mike Godwin also stated that not all Nazi comparisons are invalid.