When World War III is not far enough into the future, writers tend to make mention of later World Wars. This often used to show how mankind is doomed to repeat its past mistakes. Generally, they will be the explanation for a Crapsack World / After the End setting, or just a nasty blot in human history.
- Appleseed and Ghost in the Shell: Stand Alone Complex have both a World War III and a a World War IV in their shared Back Story. WWIV is always said to be "conventional" or "Non-Nuclear" (after WWIII exchanged a number of cities for suspiciously round lakes), and comprised several guerrilla conflicts and minor land wars before the start of either series.
- In Cross Ange, thanks to World War VII, the entire civilization of Earth is destroyed, prompting Embryo to attempt to make another world; one with no wars, discrimination, and where everyone can get whatever they want. Unfortunately, he failed at that too.
- By the 30th Century of the Legion of Super-Heroes, there had been a number of World Wars, and one Legionnaire died to prevent "World War VII" (I think, it's been a long time.)
- The Mighty Thor #371-372 features a time traveller from the future trying to prevent a chain of events that will result in World War VII.
- In A Boy and His Dog, World War IV is the apocalyptic conflict. World War III is identified as an alternate name for the Cold War.
- The Earth of Dark Planet is currently engaged in World War VI, also called the Cleansing War. Due to a bizarre interaction between a couple of WMDs, it's going to be the last one: it set off a plague that is rapidly sweeping across the planet.
- The Day After has Professor Huxley (John Lithgow) quoting Einstein regarding World War IV (see Real Life below).
- One of the sequels to Ender's Game references at least one additional World War that ended with Mecca getting nuked.
- In The History of the Galaxy, World War IV is briefly mentioned to have been brewing around the time the first extrasolar colony ships began to set off for other stars. On the other hand, the name is an artifact, as the war would involve all the Solar System.
- In The Kid Who Became President, the eponymous 13-year-old chief executive is challenged to a World War Four video game, in which World War Three eliminated all nations except a tiny dictatorship, where the game was made, and its enemy, the USA.
- The Selection is set many years after World War IV.
- The short story "The Last Flower" by James Thurber starts with World War XII having brought about the collapse of civilization, which only begins to rebuild when someone expresses concern for the world's last flower. The story ends with the next world war destroying everything in the world except for one man and one woman — and one flower.
- Lunar Chronicles: Cinder makes an offhand reference to World War IV.
- Robert A. Heinlein's The Star Beast mentions a "tank killer" gun that was a relic of World War IV.
- In the backstory to the Star Carrier series World War III was set off after Islamic terrorists nuked several major cities around the world. Then there were two Sino-Western Wars against the Chinese Hegemony, which ended with China setting three asteroids on collision courses with Earth. One, dubbed Wormwood, got through and killed half a billion people when it struck the Atlantic. As a result the Islamic states are barely tolerated by the Terran Confederation of States and China is denied representation altogether. World War VI starts in the fourth book of the series between the United States of North America and some of the other Confederation members, but is interrupted when the Sh'daar Masters break their armistice with Earth and attack.
- The Survivalist series is about a war set in the future. References are made to past wars particularly the Cold War during the 1980s.
- In World War Z, it's right there in the title, with "World War" being used to demonstrate the wide-reaching nature of the zombie outbreak (as opposed to the "first two" World Wars, which involved multiple nations fighting each other). Alternate in-universe names include "Zombie World War" and "Zombie War I" (the narrator dislikes the latter because it implies more zombie "wars" to come).
- Babylon 5:
- Subverted twice in the backstory: in 2156 the inner tensions between Earth Alliance members were getting dangerously close to cause a new World War when the sudden First Contact with the Centauri scared everyone into wiping all the troubles under the mat to make a show of unity in the face of the Centauri; by 2212 World War IV actually happens... But by this time Earth Alliance is much stronger, politically and militarily, than all its members put together, and it ends very quickly.
- The two Earth Alliance Civil Wars can be considered this.
- Doctor Who:
- The boardgame World War IV: One World, One King has it right in the title.
- Battlefield 2142 had World War IV (assuming nothing happened between Battlefield 2 and 2142) between a futuristic European Union and the Pan-Asian Collation.
- eRepublik has World Wars I to V, completely unrelated to historical ones.
- Far Cry 3: Blood Dragon makes constant referrals to a second Vietnam War (protagonist Rex Power Colt is a veteran of it). Considering it escalated all the way to worldwide nuclear annihilation, it may as well have been a World War.
- Invoked by the creator of the Mount & Blade: Warband mod Europe In Flames 1, who refers to the Thirty Years' War (the mod's setting) as "The real first WW".
- The backstory of the Splatoon series involves not just a third World War, but World War IV and V. It is during World War V that one of two global factions launched a warhead at Antarctica, causing much of the continent to melt, which didn't really help with the whole "rising sea levels from global warming" crisis. Cue mass extinction of almost every mammal on Earth, paving the way for various sea-life to evolve and become the new dominant species on the planet. Most of this information comes from the first game's art book, with the games themselves having the characters attribute the extinction of our race to global warming alone.
- In one episode of Family Guy, Peter said that the event happening would cause World War Five. Lois mentioned that there would have to be a World Wars Three and Four first, but Peter quickly dismisses it, claiming that the "beauty of World War Five is that it is so intense that it just skips over Three and Four."
- Played for Laughs in an episode of Johnny Bravo where Johnny is trapped and preserved in hair gel, allowing him to be freed 500 years in the future. When he comments on how the future looks kind of shabby, Carl's descendent states that they have had six World Wars and a couple of pandemics.
Johnny: Uh, no offense Carl, but this place is a dump.
Future Carl: After six World Wars and two global plagues, I think we've done quite nicely thank you.
- Lloyd in Space takes place shortly after World War Nine.
- Many historians retrospectively describe the Russo-Japanese War (8 Feb 1904 - 5 Sep 1905) as "World War 0"
- Some politicians and authors are under the impression that World War III was the Cold War (including the Korean War and The Vietnam War) and World War IV was The War on Terror.
- There's also the Seven Years' War (the North American theater of which was called the French and Indian War), which shared many similarities to what we now consider World War I. For this reason, many historians consider it to be the actual first world war, so if you consider them all together, we've already had five world wars.
- Further European Wars that could be considered 'World' wars: The Thirty Years' War, The Nine Years War, The War of the Spanish Succession, and The Wars of the The French Revolution and Napoleon. So that basically means that we had nine world wars! So we're pretty much worried of getting a World War X. (World War 10 if you don't understand Roman numerals)
- A popular quote, often attributed to Einstein but possibly originating elsewhere, goes, "I do not know how the Third World War will be fought, but I can tell you what they will use in the Fourth — sticks and stones!" The implication is that something, most likely nuclear weapons, will happen in WWIII that reduces humanity back to more primitive levels of technology. This also gets referenced in Deus Ex.