[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/kos_1_cover_8500.jpg]]
[[caption-width-right:350:That white is gonna ''stain.'']]
The latest, ongoing manga by Creator/TsutomuNihei, creator of ''Manga/{{Blame}}'' and ''{{Manga/Biomega}}''.

Set on the gigantic GenerationShip Sidonia, the last remnants of humanity are engaged in a seemingly HopelessWar against the monstrous Gauna. Nagate Tanikaze has lived in isolation in the bowels of the Sidonia his whole life, with only his recently deceased grandfather and Guardian pilot simulator for company. Facing starvation, Nagate journeys to the surface in an attempt to steal from a food processing plant, before being injured and captured by local authorities. Upon discovering his "grandfather's" storied past as a previously important Guardian pilot, the government puts Nagate on the fast track for elite Guardian pilot training.

What follows are Nagate's attempts to fit in with civilized society, his growing relationships with his fellow students, and his growth as a pilot in the face of the horrifying threat of the Gauna.

An [[http://www.animenewsnetwork.com/news/2013-05-16/tsutomu-nihei-knights-of-sidonia-manga-gets-anime anime adaptation]] premiered on April 10, 2014. It is being produced by Polygon Pictures, the [=3DCG=] studio behind ''WesternAnimation/TransformersPrime'' and ''WesternAnimation/StarWarsTheCloneWars'', as its 30th anniversary work. Notably, it was licensed and dubbed by Netflix as one of their "original" shows.

Not to be confused with ''Music/KnightsOfCydonia'' by ''Music/{{Muse}}''.

Be warned that this page '''contains unmarked spoilers'''.
----
!! This Manga contains the following tropes:
* AceCustom: The Type 17 counts as this for Tanikaze [[spoiler:and Hiroki]]. While rougher to handle than the Type 18 for most pilots, it's also what the simulator Tanikaze trained on was calibrated for, which means he can make it dance.
* ApocalypseHow:
** The Earth was cut in half, and humanity's desperate flight to the stars is almost Class 3. Sidonia may be the last refuge of Humanity, because contact with the other ships has been gone for almost 800 years.
** Sidonia itself lost more than 90% of its population in the relatively recent past. The vast majority of the ship's current population are descended from artificial genetic templates or are clones of the survivors, [[spoiler:including the protagonist]].
* ArtisticLicenseBiology: Humans who could photosynthesize would definitely still need to eat more than once a week. [[http://what-if.xkcd.com/17/ As Randall Munroe points out]] in ''Blog/WhatIf'', photosynthesis doesn't produce all that much energy. There's a reason plants don't move around much, let alone have complex nervous systems.
* AuthorAppeal:
** Nihei really likes his talking bears.
** Also his claustrophobic cities and UsedFuture locales.
* BattleHarem: Like it or not, the best female pilots and commanders are always attracted to Nagate.
* TheBattlestar: The Mizuki (type 1) and the Sidonia (type 2).
* {{BFG}}: [[spoiler:The magnetic linear accelerator rifles that fire the Gauna-piercing bullets]].
** The Heavy-Mass cannon would be considered one, even if tiny compared to the Sidonia ship, it still fires projectiles the size of a building dwarfing a group of Guardians.
* BigDamnHeroes: [[spoiler:Remaining First Platoon troops do it for Nagate and Izana in chapter 25]].
** [[spoiler:Nagate and Tsumugi do it for Izana in volume 9]].
* BlackBox: The Kabizashi blades are the only thing that can kill the Gauna, but no one knows how they work or how to make new ones at first.
** [[spoiler: At least until they start pumping out artificial versions of the material the Kabizashis are made form, which leads to the creation of ranged weapons. The Gauna death tolls begin predictably skyrocketing.]]
** No one has any idea how the Gauna's copies of Sidona's weapons work. This gets lampshaded with [[spoiler:Tsugumi, as no one can figure out how she flies, not even herself. Kanata, a younger chimera, is used to create a Gravitational Beam Emitter, a seemingly impossible weapon.]]
* BodyHorror: The fate of those who are captured by the Gauna.
* BreakOutTheMuseumPiece: Tanikaze initially pilots the Type 17, which was on display as a monument. Due to [[RagnarokProofing diligent maintenance,]] the older model still manages to hold its own.
* ClonesArePeopleToo:
** The Honoka sisters. Each of them has their own name (Honoka En, Honoka Hou, etc), and seem to be treated as individuals.
** This is also an important part of [[spoiler:Tanikaze's backstory. He was originally grown in a vat as a replacement body for the aging war hero Hiroki Saito, but Saito wanted to die a natural death and believed that his clone should be allowed to live his own life and so he absconded with the baby clone and raised him in seclusion as his own.]]
* ComicallyMissingThePoint: Tanikaze was a little freaked out the first time he met Lala. She thought that this was because of her claw-like Artifical Arm. ''He'' was more concerned with the fact that a ''[[EverythingsWorseWithBears talking bear]]'' had just walked up behind him.
* CoolStarship:
** The Sidonia, of course.
** The later introduced Mizuki. Yuhata has a {{Nerdgasm}} when she describes the completed warship and its armament.
* CreatorProvincialism: Many countries built their own ships but the Japanese ship, Sidonia, is the only one we see as the rest have either been eaten by Gaunas or gone off in different directions and are too far away to communicate with.
* TheCuckoolanderWasRight: [[spr: There is a significant proportion of Sidonia's population that comes to believe that [[spoiler:the Gauna are specifically targeting the ship because of the Kabizashi spears. They are dismissed as insane, up until they realize the Hoshijiro clone is [[OhCrap always looking in the direction of the Kabizashi...]]]]
** Later subverted. [[spoiler: Even though the Gauna do seem to be drawn to the Kabizashi, that didn't stop them from attacking a ship of demilitarized colonists.]]
* CyborgHelmsman: [[RidiculouslyHumanRobots Teruru]] becomes the helmsman of the new Sidonian warship, Mizuki. Beforehand, [[{{Cyborg}} Izana]] acts as helmsman of an old Sidonian cargo ship.
* DifficultButAwesome: The Tsugumori Type 17. As the direct predecessor of the Type 18, its controls are more difficult and it lacks a lot of the features which make the Type 18 a simple machine to pilot. However, in the hands of an experienced pilot like Tanikaze [[spoiler:Or his grandfather]], the Tsugumori racked up more Gauna kills than any other single unit in the series.
* EarthShatteringKaboom: Sidonia is armed with missiles capable of blowing up entire planets, from a dwarf planet to a gas giant.
* EarthThatWas: Earth was lost to the Gauna a long time ago, in what may or may not have been the events of Nihei's earlier manga ''Abara''.
* EldritchAbomination: The Gauna are massive, fetus-like creatures with the ability to assimilate humans and technology with their CombatTentacles. Some Gauna creations resemble things that are assimilated, including a Guardian [[spoiler:and its pilot]].
* EndangeredSpecies: The Sidonia's inhabitants are probably the last humans remaining in the galaxy.
* ForMassiveDamage: The only weak point on the Gauna is their core, or "True Body", which when sufficiently damaged cause them to explode. Most engagements boil down to the Guardians desperately trying to chip through the Gauna's nigh invulnerable regenerating armor to reach the weakpoint.
* FourIsDeath: All pilots of the Elite Four die in their first real battle against a Gauna. Kunato's four-man squad does not fare much better.
* {{Gainaxing}}: The anime features relatively realistic breast physics, in particular for scenes in null gravity.
* GenerationShip: The eponymous ship. There were others, but contact with them was lost.
* GenreShift: While ''Sidonia'' never stops being about a grim war, as it goes on it takes on several HaremComedy elements added to its SliceOfLife moments.
* HealingFactor: The Gauna have a rather ridiculous one, making fights with them a race against the clock to get to the weak point before they regenerate.
* {{Hermaphrodite}}: Due to some events in the setting's backstory, a third gender was created. Like some species of fish and amphibians, they eventually metamorphose into one sex or the other in order to breed.
* HonorBeforeReason: Kunato never gets over Tanikaze getting the first chance to pilot the Type 17, nor for Tanikaze getting a Gauna kill before he does. This drives Kunato to screw with Tanikaze in a number of ways, most notably [[spoiler: sabotaging Tanikaze in a fight with a Hive-Type Gauna, which results in a number of his squadmates being killed unnecessarily and [[NiceJobBreakingItHero indirectly enabling the creation of the Benisuzume.]]]]
* HumanoidAbomination: The Gauna, when they are trying to imitate humans, but they take less humanoid forms in many encounters.
* HumongousMecha: The Guardians are Sidonia's first line of defense against the Gauna.
* IdiosyncraticEpisodeNaming: Most chapters take a possessive form in their naming, usually as "(Someone)'s (Something)": for instance, "Tanikaze Nagate's Choice".
* {{Immortality}}: The captain and other members of the crew deemed essential to Sidonia's mission are kept alive indefinitely with biotechnology but because of limited resources the rest of the population is allowed to age and die at a normal rate. The truth about the Immortal Ship Committee is kept from them to keep them from getting jealous.
* InertialDampening: The Sidonia has only a limited degree of it. When they have to make sudden evasive maneuvers, massive internal damage results and people die, even though they used an EmergencyBroadcast to warn people.
* LensmanArmsRace: The Gauna continually adapt and evolve after every battle, constantly growing more sophisticated and even managing to replicate Guardian technology and tactics. Sidonia meanwhile is constantly developing new technologies and weapons in order to stay ahead of the Gauna.
* ManInWhite: Most of the Guardian pilots have white flight suits. [[WhiteShirtOfDeath Considering their survival rate...]]
* MeaningfulName: ''Gauna'' is an ancient Japanese word for a ''hermit crab''. ''Kabi'' means the germ of a rice grain.
* MileLongShip: The eponymous ship is 28 km long.
* MinovskyPhysics: Higgs/Hyggs particles play this role in the story.
* MirrorMatch: The Guardians versus Benisuzume, [[spoiler:a replica of a Guardian eaten by the Gauna]].
* MohsScaleOfScienceFictionHardness: A solid 4, at least for the humans' daily hardware.
* TheMothership: The Gauna Mass-Union ships.
* MythologyGag: Nihei recycles some elements of his [[{{Manga/Blame}} previous]] [[{{Manga/Biomega}} works]] in Sidonia, either as references or actual existing elements, such as Toha Heavy Industries, MSCF, and the Gravitational Beam Emitter, among other things.
* NeuroVault: Ochiai created one (named his 'auxiliary brain'), containing most of Sidonia's accumulated knowledge, which could only be accessed by using his brain. He then destroyed most of the original information to assure his safety (since killing him would destroy any way to access it).
* NiceJobBreakingItHero: If Kunato hadn't been so obsessed with his vendetta against Tanikaze, it's likely that [[spoiler: Toshijiro would not have been integrated by the Gauna, which would also mean the Benisuzume wouldn't exist either.]] An unusual example in that Kunato ''knew'' he was breaking it; he just wanted to pin the blame on Tanikaze.
* OlderThanTheyLook: All immortals except [[spoiler:Nagate]].
* TheOutsideWorld: Played with. For Nagate, who was raised in the innermost parts of Sidonia, TheOutsideWorld is Society. However, since Sidonia is a spaceship, it can be considered itself the inner world for all of its inhabitants, with space and the Gauna threat being TheOutsideWorld. This is part of why Nagate's such a great pilot: he's used to space and Gauna due to training a lot, so they're not so unknown to him; his real struggles come from adapting to society and other people.
* OrganicTechnology: [[spoiler:The Chimerae, biomechs grown from Gauna and human cells by Ochiai as a replacement for the Guardians]].
* PhlebotinumDuJour: The Guardians are powered by Higgs Bosons.
* PosthumousCharacter: Hiroki Saito.
* RealRobot: The Guardians count as this. Their spindly frames can't even stand up in gravity (with the exception of the [[SuperPrototype Type 19]]).
* RobotGirl: Teruru Ichigaya.
* RocketPunch: The Guardians can launch their hands off on a towline and grapple onto things with them. Tanikaze manages to weaponize this to defeat the Red Sphingida after it destroys his gun by taking a Gauna-piercing bullet between his fingers and launching it through her body at point blank range.
* SceneryPorn: It's a Creator/TsutomuNihei manga. It's his trademark. In fact, chapters often start with travel-guide style images titled "Sidonia's 100 Sights" that show off the scenery.
** SceneryGorn: Among them is a sketch of a possible Gauna-occupied Sidonia. [[spoiler:It's not too far from what the Gauna recreates in their collective ship in Ch.57, though that is quite beautiful]]. Chapter 0 shows the successful Gauna attack on Sidonia's residential area which happened a century ago.
* ShoutOut: In the episode where they decide to destroy a Gauna-infested planet, one fansub group translated the command as [[{{Warhammer40000}} "Exterminatus"]].
* SparedByTheAdaptation: [[spoiler: Izana's limbs, as the anime leaves her considerably less perforated]].
* SpiritualSuccessor: The series had an early prototype in the form of an obscure one-shot manga called ''Winged Armor Suzumega, [[EitherOrTitle or]] The Armored Insects Sphingidae''.
* StarfishAlien: The Gauna are a weird sort of fetus-like creature with a central "main body".
* StealthSequel: To ''Abara'', possibly.
* SuperPrototype: Due to being TheAce, Tanikaze gets first run of the Type 19 and (eventually) Type 20 Guardians.
* TranshumanTreachery: Played with. Ochiai aside, almost every member of the cast is genetically and/or cybernetically modified in some way, but they're still pretty normal and ordinary by our standards.
* TheUriahGambit: The captain wants Tanikaze dead for reasons not immediately explained and to this end orders him to fly in every single mission against the Gaunas in the hope that they'll eventually kill him. [[spoiler:This backfires as not only Nagate always survives but he eventually becomes Sidonia's greatest hero]].
** [[spoiler:It was actually due to the immortal ship committee. Tanikaze is an immortal and they couldn't tolerate an immortal outside of the committee hierarchy, so as a compromise to outright killing him, the captain agreed to put him on what should have been a suicide mission as a compromise. As long as he keeps succeeding, he can live. Of course once the committee is offed in a coup by the captain, he's no longer required to attend missions but tends to do so anyway due to having become used to being a hero.]]
* UsedFuture: The residential area of Sidonia is filled with dilapidated buildings and massive amounts of old piping. Much of the clothing the characters wear is patched up. The Sidonia's hull is cratered and pitted from hundreds of years of minor impacts. Even the functional technology like spacesuits, hulls, and even the walls of the bridge are covered in old scoff marks.
* WhiteShirtOfDeath: Most pilot uniforms are all white, as are the Guardians themselves. Considering the attrition rate versus the Gauna...
* WhoWantsToLiveForever: After the gruesome Fourth Gauna Defense War, Hiroki Saito suffers from longevity-triggered dysfunction and seeks to die in peace. He does not take it well when the captain tries to extend his immortality against his wishes.
* YouGottaHaveBlueHair: Teruru Ichigaya's hair is literally blue. Justified because she is an artificial life-form.
----