Alternate history or alternative history is a genre of fiction consisting of stories that are set in worlds in which history has diverged from the actual history of the world. It can be variously seen as a sub-genre of literary fiction, science fiction, and historical fiction; different alternate history works may use tropes from any or all of these genres. It is sometimes abbreviated AH. Another occasionally-used term for the genre is "allohistory" (literally "other history").

In writing an alternate history, the author makes the conscious choice to change something in our past. According to Steven H Silver, alternate history requires three things: 1) the story must have a point of divergence from the history of our world prior to the time at which the author is writing, 2) a change that would alter history as it is known, and 3) an examination of the ramifications of that change.

Several genres of fiction have been confused as alternate histories. Science fiction set in what was the future but is now the past, like Arthur C. Clarke's 2001: A Space Odyssey or Nineteen Eighty-Four , are not alternate history because the author has not made the conscious choice to change the past. Secret history, works that document things that are not known to have happened historically but would not have changed history had they happened, is also not to be confused with alternate history.

Alternate history is related to but distinct from counterfactual history—the term used by some professional historians when using thoroughly researched and carefully reasoned speculations on "what might have happened if..." as a tool of academic historical research.

Since the 1950s, this type of fiction has to a large extent merged with science fictional tropes involving cross-time travel between alternate histories or psychic awareness of the existence of "our" universe by the people in another; or ordinary voyaging uptime (into the past) or downtime (into the future) that results in history splitting into two or more time-lines. Cross-time, time-splitting and alternate history themes have become so closely interwoven that it is impossible to discuss them fully apart from one another. "Alternate History" looks at "what if" scenarios from some of history's most pivotal turning points and presents a completely different version, sometimes based on science and fact, but often based on conjecture. The exploration of how the world would look today if various changes occurred and what these alternate worlds would be like forms the basis of this vast subject matter.

In French and German, alternate history novels are called uchronie. This neologism is based on the prefix u- (as in the word utopia, a place that does not exist) and the Greek for time, chronos. An uchronie, then, is defined as a time that does not exist, a "non-time." This term apparently also inspired the name of the alternate history book list, uchronia.net.

A Brief List of Popular Alternative History Fiction Works:

• 1990. The Difference Engine by William Gibson and Bruce Sterling, Charles Babbage's Analytical Engine takes on the roles of modern computers a century early.
• 1990. The World Next Door by Brad Ferguson, people from a world that experienced nuclear war in 1962 interacts with people from a world that did not.
• 1990. A World of Difference by Harry Turtledove, the 4th planet of our solar system, named Minerva instead of Mars, is larger and contains intelligent alien life.
• 1992. Fatherland by Robert Harris, set in the 1960s in a Germany which won World War II.
• 1992. The Guns of the South by Harry Turtledove, the Confederate Army is supplied with AK-47s by early-21st century white supremacist South African time-travelers.
• 1992. Konpeki no Kantai by Yoshio Aramaki. Japan becomes a stronger naval power thanks to Admiral Isoroku Yamamoto who appears several years in the past despite dying in World War II. Later adapted into an OVA series.
• 1993. Anti-Ice by Stephen Baxter, explosive scientific discovery made in the 1850s advances technology.
• 1993. Aztec Century by Christopher Evans, Cortez changed sides at the onset of the Conquistador era in the early sixteenth century, leading to the repulsion of Spanish invasion and occupation of Central America.
• 1993. Down in the Bottomlands by Harry Turtledove, at the end of the Miocene period, the Mediterranean stays dry to the present day.
• 1993. Elvissey by Jack Womack, a dystopian 2033 where a Machiavellian multinational corporation has plans for world domination.
• 1995. 1901 by Robert Conroy, depicts a hypothetical war between Germany and the United States at the start of William McKinley's second term as President.
• 2001. After Dachau by Daniel Quinn, Germany wins World War II and eventually all non-whites are killed off.
• 2001. The Children's War by J.N. Stroyar, in World War II Germany does not attack the Soviet Union and develops a nuclear weapons program.
  • A Change of Regime (2004)
• 2001. The Haunting of Alaizabel Cray by Chris Wooding, Victorian London is overrun by the wych-kin, demonic creatures that have rendered the city uninhabitable south of the river, and which stalk the streets after dark.
• 2002. Ice by Shane Johnson, the Apollo 19 mission suffers a major system failure, forcing its crew to strike out on their own.
• 2002. The Peshawar Lancers by S. M. Stirling, in 1878 a meteor shower devastates Europe and North America forcing the European empires to relocate their population to their colonies.
• 2002. Ruled Britannia by Harry Turtledove, the Spanish Armada conquers England and forces Shakespeare to write a play about Philip II. At the same time he is secretly writing a play for the English underground resistance.
• 2002. The Years of Rice and Salt by Kim Stanley Robinson, the Black Death of the 14th century kills 99% of the people in Europe and over the next seven centuries, India, China and the Islamic world come to dominate the planet.
• 2003. Collaborator by Murray Davies, set in a Nazi occupied Great Britain centering around a former POW and life in occupied Britain.
• 2003. Conquistador by S.M. Stirling, an inter-dimensional gateway is discovered in California, which gives access to an alternate Earth in which the empire of Alexander the Great flourishes, and where Europeans never discovered America.
• 2003. In the Presence of Mine Enemies by Harry Turtledove, a family of secret Jews hide in Berlin two or three generations after a Nazi victory in World War II.
• 2003. Roma Eterna by Robert Silverberg, the Red Sea did not part before Moses and as a result, the Roman Empire grew and prospered without the influence of Christianity.
• 2004. Airborn by Kenneth Oppel, the airplane is never invented and instead airships are used for travel.
• 2004. The Plot Against America by Philip Roth, Charles Lindbergh is elected President of the United States in 1940 and collaborates with Nazi Germany.

For more information on the genre, visit the Wikipedia page. For more Alternate History Fiction, click here.