Alternate history is a speculative fiction genre that describes a historical "what if" with some speculation about the consequences of the different result.
Other names which may apply to the form include alternative history, allohistory, counterfactuals, if-worlds, uchronia and uchronie, parallel worlds, what-if stories, abwegige geschichten, etc. Whatever it is called, alternate history involves one or more past events happening differently and includes some amount of description of the subsequent effects on history. Two common themes include "What if the Nazis won World War II?" and "What if the Confederacy won the Civil War?"
Alternate history may appear in novels, short stories, scholarly essays, comic books, movies, television shows, plays and elsewhere.