Space Nazis

Space Nazis are a common theme in sci-fi and fantasy dealing with the aftermath of World War II or the evils of the third reich when it was in its prime - the genre is also based on actual conspiracy and fringe scientists that believe Nazi Germany had contact with aliens and may of even evaded justice via the use of advanced technologies (widely ridiculed with the "Nazis on the moon" subtype of this genre).

The usual theme is of surviving Nazis (or their descendents) living in or colonizing space - yet still retaining their loyalty to the third reich and Hitler's ideals, variants can also deal with alien or exotic weapons being in the hands of the actual third reich during their power (or in alternate time-lines where the wars are either still being waged or the Nazis succeeded in their conquest).

The term can also be used (sometimes negatively) for alien / fantastical races in fiction that are clearly inspired by the Nazis.