Generation Ships

If the laws of physics don't allow Faster Than Light Travel, it's going to take a long time to colonize the stars. If you can't get close enough to lightspeed to take advantage of Time Dilation, don't have the medical technology for functional Immortality, and you don't want to resort to suspended animation/hibernation (or, in more recent SF, Brain Uploading), you're not going to see the destination yourself -- it may be your grandchildren, or their grandchildren, or their... You get the idea.

This doesn't have to wind up as a City in A Bottle, but frequently does (and did in what is perhaps the first story to use popularize this trope, Robert A. Heinlein's "Universe"). Several examples of Generation Ships are listed on that page.

Generation Ships are great settings for sociological comment: the author has a nice sealed pressure vessel to play out their theories or critique existing cultures.

A Generation Ship is almost always a Starship Luxurious -- it's got to sustain the equivalent of an entire ecosystem, whether it does so with rivets-and-bolts machinery or with an actual terrarium-style recreation of a full-fledged habitat.

Sometimes, a Generation Ship doesn't have a destination -- it's an interstellar trade ship, connecting isolated colonies or installing the Hyperspace Gateways that will allow FTL expansion and exploitation, in which case the populace are usually Space People. Occasionally, the generation ship will arrive to discover that someone developed an FTL drive while they were en route and the world they were going to colonize already has a few million people on it.

Has nothing to do with fandom Shipping older and younger characters.

Anime

 * Megazone 23 (the first two installments).
 * The official backstory for Turn a Gundam says that
 * We get to see the beginnings of this process in Gundam SEED. The Genesis System used at the end of the series was originally created as a laser propulsion/nuclear pulse hybrid engine meant to be attached to colonies to facilitate their exodus from the solar system & thus escape the conflict between Naturals & Coordinators, before Patrick Zara decided to repurpose it as a doomsday weapon & tried to use it to end the war in a more direct manner. In the Gundam SEED Astray manga the heroes actually help a neutral colony afix one to use for its intended purpose.
 * City 7 of Macross 7 was a rare example of a faster than light generational ship.
 * Macross in general has these, with humanity deliberately spreading itself out to avoid species-ending disasters like the end of the original series. Macross Plus is actually the only series set after the original without one.

Comic Books

 * A Fantastic Four story had the FF come across an alien race who had been traveling so long that they had adapted to their ship's artificial environment and could not survive on a planet. When Reed reveals this to their captain, he doesn't take it well. Ultimately the next leader decides to keep the truth from her people for the greater good.
 * He doesn't take it well because the religion he follows find the idea that they are not as their god created them but have evolved abhorrent. He commits suicide. Incidentally all the aliens look the same. It's a bit of a surprise to find the first mate is female, the captain's wife, and that her ancestors knew all along but kept it a secret.
 * The Levians were another comics race who lived on a generation ship and encountered Earth superheroes.

Film

 * MST3K alumnus Space Mutiny tries to use this trope, but it doesn't really make much sense. I mean, space pirates and rapid space travel also seem to exist... Of course, you could argue the Southern Sun launched before faster travel was developed...
 * In Pandorum, the Elysium becomes this after one of the crewmembers.

Literature

 * Endless Universe, by Marion Zimmer Bradley, is an example of "Generation Ship Planting FTL Gates".
 * Paradises Lost, by Ursula K. Le Guin, focuses on the generations who grow up on the ship.
 * The Hitchhikers Guide to The Galaxy, spoofed by the B Ark. The inhabitants think they're going off to colonise a "less doomed" planet - in fact, everyone else on the not-doomed-at-all home world just got sick of them.
 * Ironically, the people who stayed on the supposedly doomed planet die from an infection spread by unsanitized telephones, as the B Ark included all the telephone sanitizers.
 * In Norman Spinrad's Riding The Torch, the remains of the human race in its entirety had to leave Earth after a nuclear cataclysm, flying Bussard ramjet ships ("torchships") in search of a habitable planet. Slowly they use the resources gained from the void by Bussard engines to develop an entire civilization under the guise of an ever expanding fleet of torchships.
 * Bernard Werber's "Le papillon des étoiles" focuses on a generation that, over time, forgets its original purpose and origin. The generations eventually rediscover violence and weapons, civilization devolves into a middle age-esque tyranny until, by the time the ship reaches its destination, only 5 people are alive on the ship, and only 2 manage to leave it safely.
 * The title vessel in Rendezvous With Rama appears to be one of these in the original novel. The sequels provide a different and much less satisfying explanation for its existence.
 * Orphans Of The Sky by Robert A. Heinlein has a massive generation ship whose inhabitants have forgotten their origins and fallen into barbarism, yet the ship still functions after centuries of neglect (albeit with an assist from Cargo Cult maintenance procedures). Guess they don't make them like they will have used to.
 * The New Frontiers in Methuselah's Children was a Generation Ship which was later upgraded with a FTL Drive.
 * The Galactic Whirlpool is set in the Star Trek Expanded Universe, where the Enterprise discovers a generation ship launched just before the Last World War, whose inhabitants have-- surprise surprise --forgotten their origins and descended into barbarism.
 * The most extreme example -- in Larry Niven's Ring World, the Fleet of Worlds is the Puppeteers' entire planetary system converted into a generation ship to flee the galaxy.
 * The Pak also did this with when they colonized Earth and the Ringworld itself.
 * In addition to that ultra-long journey (half a million years), the Pak have ships that would be generation ships for a species with less incredible lifespans - Phssthpok flies a ship for 1200 years (ship's time), alone.
 * Second Genesis has a Living Ship called Yggdrasil that takes a journey between galaxies; it would normally be called a generation ship, except its inhabitants have discovered Immortality, and so a few centuries of relativistic travel is not much of a burden.
 * Niven and Pournelle's Footfall has the Fithp use a hybrid generation ship to reach Earth: most of the passengers are in stasis, but necessary maintenance and piloting is carried out by successive generations of crew. The result is a significant culture clash between the 'Shipborn' and the defrosted original generation.
 * In Alastair Reynolds' Chasm City, the planet of Sky's Edge was settled by 5 generation ships traveling at 6% lightspeed. There are at least 4 generations on the ship.
 * Gene Wolfe's Book of the Long Sun is set within a vast generation ship called the Whorl. It isn't quite a City in A Bottle, because the characters are vaguely conscious that there is an "outside" (the oldest character in the books has some faded memories of living there)... but they have no real idea what outside actually means, and none of them expect to ever experience the outside.
 * Rob Grant's Colony deconstructs this somewhat. Various systems go wrong (notably the eugenics program determining who is allowed to mate with whom, and the career-allocation system), so the later generations are hopelessly inbred, illiterate and unqualified for their jobs.
 * Not quite a deconstruction as things going horribly wrong is the normal state of this trope.
 * Eric Flint's Slow Train to Arcturus with the added bit most of the ship consists of misfits people wanted off Earth in their own sealed habits. Including Neo-Nazis, Space Amish, Radical feminist genetic engineers, Native Americans, and extreme sports enthusiasts, and North Korea. A Plot Tailored to The Party follows with a message about needing each other to survive (well at least needing everyone except for the Neo-Nazis and the leaders of the North Korean group).
 * The planet Martine was settled by one of these in Crest of the Stars and the Abh's original home was one as well before they cracked the FTL issue.
 * Generation ships (called longliners) are used to carry messages and trade between planets in Frederik Pohl and C. M. Kornbluth's "Search the Sky". They're pretty horrid: while they don't quite forget their mission, the people on board end up suffering fairly severe mental retardation (it's not too clear why, possibly a lack of intellectual stimulation?), and they're kept from overpopulation by massive infanticide. But every place in that book is in horrible shape: it's a horribly Darker and Edgier world before it was popular. The longliners appear to use liquid fuel rockets, which is what the Saturn V rockets used; in 1970, with a millionth of the distance a Longliner travels.
 * In Octavia Butler's Liliths Brood, the Oankali travel on these as they go from world to world making genetic trades. Also a Living Ship.
 * In Brian Aldiss' Non-Stop: A plague on a generation ship reduces the passengers to barbarism: they lose all idea of who they are or even what a spaceship is. The bioengineered plants go into overdrive, turning the ship into a jungle, increasing the sense of obscuration and isolation. The reader's first clue as to what's going on is when the jungle turns out to have bulkheads.
 * Non-space example: in Perdido Street Station, the khepri residents of New Crobuzon are descended from refugees who'd fled a mysterious disaster on their native continent. As their ramshackle ships took decades to cross the ocean, and thousands of the refugees died en route, some khepri vessels technically invoke this trope by having only ship-born crew members left on board when they reached land.
 * Another non-space generation ship is Armada from The Scar by China Mieville, which is a floating city build by connecting hundreds of regular ships. It doesn't have a permanent destination and it is not meant to ever reach land (as it is a piratical society), but has a permanent population that has lived in the city for generations.
 * Harry Harrison's Captive Universe: A Generation Ship with a seamless environment is launched: by design the highly repressive, extremely stable Aztec cities onboard believe themselves to be in an inaccessible river valley. The ship tenders are if anything more rigid and religious: an extraordinary asceticism rules their lives and repairs are sacred rituals.
 * The title species in Alan Dean Foster's Quozl seek out new habitable worlds in these.
 * Simon Hawke's The Whims of Creation is set on one, generations after humanity has left the Earth That Was.
 * Common FTL travel powerful enough to at least get around one's own galaxy makes these relatively uncommon in the Perry Rhodan universe, but they're not unknown. Ships (and space stations) intended for really extended missions, such as some undertaken by mortal helpers of the setting's Powers That Be, may be designed to fit the trope, and suitable vessels have turned into this purely by accident, as happened to the SOL when its cosmic odyssey dragged out longer than expected and the shipborn generation started to have their own ideas about what uses their 'home' should be put to. Stretching the definition of "ship" to the limit, a major significant example would be the cosmic swarms, literally mobile star clusters whose multi-species 'crews' quite naturally were born, lived, and died on the worlds orbiting said stars while going about their assigned task of aiding the spread of intelligence throughout the universe.
 * In Poul Anderson's Tau Zero, the Leonora Christine is only supposed to take 5 years of time (relative to the passengers onboard) to reach Beta Virginis. It becomes a generation ship, though, when its deceleration unit breaks down.
 * Andrey Livadny's novel Ark is set aboard the title ship, a Moon-sized (literally, as it is the hollowed-out Moon with engines attached) ship built by humans to fly around the galaxy and collect samples of intelligent life to eventually bring back home. These "samples" were put into special habitats modified to the conditions on their homeworlds, even including artificial suns. There was also a human habitat for the families of the crew. Then an onboard cataclysm killed most of the senior officers and damaged many cybernetic systems, isolating the habitats from the command module and each other. Millennia later, the ship is falling apart with disrepair, as the human descendants have regressed into a near-Medieval state and forgot their origins. The only hope is a boy who has been a Human Popsicle since the cataclysm and is the only one who can regain access to the command module and direct the ship to a habitable planet. The ending reveals a possible.
 * Also, cats have evolved into intelligent humanoids.
 * Interestingly, this is one of the few novels by Livadny that don't include some form of Faster Than Light Travel.
 * In François Bordes's novel Fleeing Earth (Terre en fuite, written under the pen name Francis Carsac), the Nested Story reveals that the people of the Second Civilization of humans (after most of us die out in another Ice Age) discover that the Sun is about to go nova. Since they can't build enough ships to fit everyone from Earth and Venus (terraformed and settled), they instead decide to move both planets by building giant "space magnets" at the poles. The original plan is to move them to the Outer Solar System, hide behind Jupiter, and return once the Sun settles down. However, they discover that the Sun will not return to its yellow dwarf state after the explosion and have to move to a new system. Thus both planets become giant generation ships, although the interstellar journeys only take several decades thanks to the "space magnets" accelerating the planets to 80% of the speed of light.
 * Domingo Santos' story The First Day of Eternity (published in Analog) concerns a ship, the Diaspora 32 that has been traveling for 721 years.
 * The backstory of Kevin J. Anderson's The Saga of Seven Suns involves 11 generational ships sent out into space. None of them reach their destinations, however. Nine are found by an alien race who use their FTL technology to take them to habitable planets. Another ends up colonizing whatever asteroids and other non-terrestrial environments they can find becoming Space Gypsies. The other one is assumed to be lost until it is discovered that
 * In "Thirteen for Centaurus" by J. G. Ballard, the action takes place on a generation ship
 * The Clockwork Rocket by Greg Egan takes place in a universe where physics is different and Time Dilation works in reverse -- the faster you travel, the more time passes from your perspective. The protagonists, seeing an oncoming disaster that they don't have the technology to prevent, build a generation ship so their descendants will have enough time to develop it while only a few years pass on their world.
 * Molly Glass' "The Dazzle of Day" a generation ship populated by Quakers nears a system where they could possibly settle. Much of the action of the novel deals with the decision of whether to stop here or go on. Since all decisions are made by the Quaker practice of Consensus, this is a complex task.
 * In Empire From the Ashes, the planetoid-class ships have perfectly good FTL that can get them around to most places in less than a year, but they're still set up as generation ships because they oftentimes go on long tours of duty and it's considered necessary for the health of the community to have children born and growing up as they would be on a planet. Of course, being what they are, these ships have crews in the hundreds of thousands and provision for natural increase up to doubling.
 * Across the Universe is set on a generation ship called the Godspeed, which is on a journey to a habitable planet that will take hundreds of years to complete. While a lot of the colonists elected to be turned into Human Popsicles for the duration of the trip, there was a need for an active crew to perform maintenance. Thus, many generations have lived and died on the Godspeed as it slowly makes its way towards its destination.
 * One is briefly visited in Bill the Galactic Hero on the Planet of Ten Thousand Bars.
 * In The Tomorrow Log by Sharon Lee and Steve Miller,.
 * The short story "Schism," set in the Elite universe, examines what happens when a homegrown Cult Colony inside a Generation Ship that has been out of contact with human civilization for centuries encounters another derelict vessel in the void of space.
 * Robert Reed is a fan of this trope. His short story, The Children's Crusade, is about a simulation of a crashed alien starship on Mars - in which the organic passengers are essentially cargo, while the robotic crew controls the ship. Chrysalis has the last lifeboat of humanity traveling through the galaxy to collect species before they destroy themselves, with immortal robots controlling the ship. The Winemaster has a Buick being used essentially as a generation car - the transhuman / post human residents are so small and live so quickly that an hour real time is like a year to them; several generations go by in the trip from a northern state into Canada.

Live Action TV

 * The Starlost had the entire series take place on a huge generational ship with different biomes sealed off and having forgotten it was a ship. Ben Bova and Harlan Ellison wrote books about the Executive Meddling and the novelization.
 * Terra Venture in Power Rangers Lost Galaxy.
 * Which got lucky and reached an inhabitable planet complete with primitive Human Aliens inhabitants within a year or so.
 * It was the same planet that the team had been warped to in the pilot to receive their powers and was the home of the team's resident Human Alien. So, not so much luck as destiny.
 * It appears the 'Verse was colonized by these in Firefly.
 * Star Trek the Original Series has "For The World Is Hollow And I Have Touched The Sky".
 * And "By Any Other Name" had a faster-than-light generation ship that the Kelvans used for the immense journey between galaxies.
 * Silly of them not to have gone just slower than light and have made the trip in a (subjective) day.
 * If they had gone slower than light, it would have taken them over 2 million years to get to an Andromeda Galaxy that had been uninhabitable since the 123rd century due to increasing radiation levels.
 * The Star Trek Voyager episode "The Disease" has a generation ship which is over four hundred years old.
 * In Star Trek the Next Generation, this was the original concept of the Galaxy-class ships like the Enterprise-D. In practice, they Travel At The Speed Of Plot and between that and the amount of combat scenarios encountered, the idea of Enterprise-as-a-family-poting was dropped from future iterations of the franchise.
 * In an episode of Star Trek Enterprise, the enterprise . The Enterprise then becomes a Generational Vessel
 * Janeway often wonders whether "Voyager" will become such a ship itself: the original return estimate is 70 years, after all.
 * The Magog Worldship on Andromeda.
 * The Australian series Silversun used this. As the journey to the new planet would take many years, most of the crew were adolescents and teenagers, so that there would be at least some crew still around when they got to the planet. A lot more people are in cryogenic stasis.
 * Stargate Atlantis had the Travelers, a race of space nomads who live entirely on self-built ships in order to avoid being culled by the Wraith. Despite their strict population control, they don't have the resources to build new ships any more and were forced to abandon some people on planets where the Wraith culled them. This was why they kidnapped Shephard in their introductory episode: they found an Aurora-class Ancient battlecruiser and needed his ATA gene to get it operational since the ship could carry thousands. They lost one of their ships in the battle above Asuras and with the Replicators gone, they settled on a planet... then the settlement and the Aurora was nuked in the final season when their Stargate exploded.
 * The Destiny from Stargate Universe could be seen as a generation ship, in that it not only took the resources of an entire generation to build, but wasn't even boarded until over a million years after it launched. While it is a ship on autopilot and flies through FTL, the scope of its mission is so large that the Ancients who built it could not have hoped that they or their children would be alive to see that mission to its end.
 * The Novus civilization, founded by the crew of the Destiny over 2000 years before the crew actually encounters Novus (long story), dedicated its resources to building a fleet of ships for its millions of citizens so that they could evacuate their dying world. They will reach their destination in a few hundred years (in stark contrast to the 10 days Destiny needs to cover the same distance with its FTL).
 * The Doctor Who episode "The Beast Below" has the entire United Kingdom (minus Scotland) on a single spaceship, searching for a new home after the Earth becomes uninhabitable. The discovery of just how this massive ship is travelling through space with the engines apparently off forms the main mystery of the episode.
 * And the Doctor claims it is just one of many, with each country building their own ship. The others are just not shown.
 * Much earlier, First Doctor serial The Ark, had the title spacecraft serving as both a generational ship for its crew (of both humans and subservient aliens), and as a Human Popsicle-stand for the remaining billions of humans and subservient aliens, since a ship that could carry both species in their entirety would've been far too massive to build (or move).
 * The Space 1999 episode 'Mission of the Darians'. The crew of Moonbase Alpha respond to a distress call from a 20 mile long ship on a 900-year voyage.
 * The Red Dwarf housed a breeding population of life-forms descended from a single pregnant cat for about 3 million years, long enough for them to evolve sapience and build their own arks to leave.

Music

 * Blake Hodgetts' song Boundless? concerns a generation ship gone City in A Bottle.

Tabletop Games

 * The Eldar Craftworlds in Warhammer 40000. They do have FTL-capabilities, but since they are essentially spacefaring colonies designed to house the survivors of the Fall, they count.
 * Most human vessels as well. Military craft and the ships of rogue traders have warp drives. Everyone else does it the hard way. It takes a few decades for short trips, each way.
 * Actually, virtually all Imperial ships (interstellar ones that is) are this - their bigger ships frequently have issues with the spontaneous development of small civilisations in less well-known parts of the hulls. Also, with mixed-gender crews in the thousands on a ship that serves for millennia, it is sort-of inevitable.
 * The early science fiction game "Metamorphosis Alpha" from TSR was set on one of these. It was reworked later as the Amazing Engine setting book "Metamorphosis Alpha To Omega".
 * GURPS: Spaceships has the uses the traditional concept for the Universe and Endeavor. The third ship is the Magellan which carries 20 thousand people in luxury at FTL speeds, allowing for ridiculously long trips.

Theater
""You mean to tell me you've eaten all the great scientists and engineers who were going to build this new world? Didn't anyone protest?"
 * Parodied in one Australian play (forgot the name, sorry) where the crew of a Generation Ship fall into barbarity and think that the human popsicles are the equivalent of frozen food. When the last remaining colonist wakes up early, he's not to impressed.

"Of course they did. But we ate them anyway!""

Video Games

 * The entire world of Phantasy Star 3 takes place on one of these. Later, in Phantasy Star 4, the heroes find the wreckage of one such ship that had fallen from the sky.
 * To elaborate a little bit, these things were basically planetary escape pods, sent out when Parma exploded. Didn't go too well, though - some got lost, some were caught in the explosion and destroyed.. the one mentioned above was crippled in the escape and suffered the nasty fate of getting stuck in a decaying orbit around Motavia.
 * In Wild Arms 5 the Veruni spent most of the 10,000 years they wandered for a new home on their ship, Locus Solus. By the time the Veruni have settled on Filgaia the ship itself is considered by many of the Veruni to be their homeland, and they revere it to the point of calling the ship Mother.
 * According to the manual, you can occasionally run across these in the original Elite; however, that's the only place they exist in that game. In the expandable remake Oolite on the other hand, you can really run across them with the right OXP.
 * The titular Marathon colony ship.
 * In Mass Effect the entire quarian species dwells in a massive flotilla consisting of thousands of this trope due to being driven off their original planet. The fleet isn't going anywhere in particular, but the trope still fits.
 * In fact, the Migrant Fleet is actually the largest fleet in known space. They just don't have any planets where they could off-load their civilians.
 * Homeworld has this in the backstory: when the Hiigarans were exiled, the entire civilization was packed into a fleet of identical FTL-incapable generation ships that crossed half the galaxy on sublight until the last four or so reached Kharak. Some of them broken off and became the Kadeshi, a society who camped out in a nebula and gave everyone they met a choice: join or die (the ship is plundered and destroyed in both cases). By the time their distant siblings who made it to Kharak found them, the Kadeshi were religious fanatics who worshipped the nebula and talked in a Creepy Monotone. Oh, and according to the Expanded Universe, they were also Evil Albinos. One of the generation ships is still floating in the center of the nebula, unmanned and slowly spinning in place.
 * Arguably, the planet in Might and Magic 7 has turned into one of these: They have regressed to roughly medieval levels of technology,.
 * Building one of these and sending it to Alpha Centauri is one of the ways to win in Civilization.

Webcomics

 * Unity is set on a generation ship several million years in the future.

Web Original

 * In Orions Arm a few early colony ships were these, but smaller and faster sleeper ships had a tendency to reach the destination systems earlier. They're currently used as mobile habitats, freighters, and wormhole layliners.

Western Animation

 * The Axiom from Wall E is one of these, sustaining human life in space after the Earth has become uninhabitable.
 * Subverted in that it wasn't meant to be. The humans were supposed to be aboard for just a few years, while the Wall-E units cleaned up the earth. The Buy-n-Large president, however, deemed the Earth permanently doomed and ordered the Autopilot to keep them in space forever. He turned out to be wrong, but it's 700 years before the first plant life reappears on the planet.
 * Used in the Galaxy Rangers episode "Lord of the Sands." The descendants of an Earth sleeper ship had crashed on a desolate planet and formed a tribal civilization roughly seventy years earlier. Something had wiped out the adults, so the tribe was mostly comprised of adolescents - led by a rogue Crown Agent.
 * After Earth is destroyed at in Titan AE, most of the surviving humans turn their ships into this. Fortunately, this only lasts 15 years until.