Fiction set in a world whose history branches off from our own, which may or may not have science-fictional or fantasy elements
Alternate history is a form of speculative fiction depicting a world in which history has diverged from our history. Alternate history stories depict an alternate timeline that starts from a point of divergence (POD) which may or may not be explicit in the story.
Alternate history sometimes involves time travel or inter-timeline travel, but can also be self-contained.
- The alternate history list (a good resource to identify alternate history stories or find alternate histories with a particular point of divergence)