The ''Helliconia'' Trilogy, by Creator/BrianAldiss, is an epic sci-fi series that follows the lives of the HumanAliens that live on the titular planet. The trilogy's timeline stretches a thousand years, following certain influential characters as civilizations rise and fall. Set in a [[BinarySuns binary star system]], Helliconia has "years" of two different lengths. The "Small Year", about 480 days, is how long it takes for Helliconia to orbit its main star Batalix. The "Great Year", in which Helliconia and Batalix both orbit the much larger star Freyr, is over 1,800 Small Years.

Helliconia spends about half of the Great Year as an [[SingleBiomePlanet ice planet]], as Batalix is much dimmer than Earth's sun[[note]]or, more accurately, Helliconia is farther from Batalix than Earth is from our sun[[/note]] and its highly elliptical orbit means that Freyr is too distant to provide any warmth. As the Great Year proceeds, though, the much larger and brighter Freyr comes into play, causing gradual but severe climactic changes. As such, Helliconia goes though extended "seasons" lasting centuries.

Despite being [[AllPlanetsAreEarthLike relatively Earth-like]], Helliconia is host to multiple intelligent species, the most prominent of which are Humans and [[ALoadOfBull the Phagors]], mankind's primary antagonist.

The series picks up as Helliconia is transitioning from it's long Winter into Spring. As the planet begins warming up and becomes more hospitable, mankind begins to develop civilization and become dominant in the world.

The trilogy comprises these books:
* ''Helliconia Spring''
* ''Helliconia Summer''
* ''Helliconia Winter''

!! This series provides examples of:
* ALoadOfBull: The Phagors, the other sentient race of Helliconia and constant antagonists to mankind, resemble minotaurs.
* AlienSky: As Helliconia is in a binary star system, this is a given. Brian Aldiss goes to great lengths to depict the movements of the stars in Helliconia's sky accurately, including how the orbital dynamics of the Helliconia-Batalix-Freyr system would play out from the perspective of Helliconia.
** Batalix, appearing larger in the sky, actually eclipses Freyr several times. Think about that for a second -- imagine our sun being ''eclipsed by another sun''.
* AlternativeCalendar: The world has 480 days, so the calendar is unsurprisingly different: The year has ten tenners (not months, since the planet lacks a moon), with six weeks of eight days. The day has 25 hours, each hour has 40 minutes and each minute 100 seconds. Quite metric. The digital watch shows three different times. In one time, the minute seems to have at least 80 seconds - but the other two don't.
* BizarreAlienBiology:
** The Phagors have inverted organs; their intestines are above their lungs. They also have yellow blood.
** The Hoxneys, resembling zebras or horses, hibernate in the long winter as crystalline beings.
** There's also the Barsimmip Trees -- which are actually very large, subterranean, and hollow.
** Wutra's Worm -- [[SandWorm A gargantuan worm]] with a lifespan as long as the Great Year. Goes through several drastic metamorphoses as the Great Seasons pass; at one point, a Worm will actually split into two smaller worms with wings, which then take to the sky.
* BizarreSeasons
* BolivianArmyCliffhanger: The first book ends as [[spoiler:the village/city-state where the majority of the plot takes place is about to be wiped out by an invading army of Phagors.]] The reader is LeftHanging, since the second book begins in a completely separate country, with new characters. Made even worse as the reader soon finds out [[spoiler:that it's over 300 years later, and nothing about the events of the first book are even really known other than an off-handed comment about some "fire" there years ago.]]
* CallARabbitASmeerp: Averted, since the various non-obviously-alien animals in the series are described pretty much as you would expect. There are sheep, pigs, and even terrestrial plants such as wheat. However....
* CallASmeerpARabbit: ...they're never described in enough detail to tell either way.
** Further confused by the obviously-alien-looking creatures and fauna of Hellliconia that exist alongside the more recognizable ones (with unique obviously-alien names to boot).
* DumbIsGood: In the first novel, the major philosophy of Aoz Roon, leader of human village where the plot takes place. He discourages too much learning, since he doesn't want to have any "idle mouths" to feed (i.e. teachers, philosophers, etc)
* EndlessWinter: The Trilogy, set on the planet of the same name, involves a world in a highly elliptical orbit around its sun. Its summers last centuries, but its winter lasts for ''over a thousand years''. [[spoiler:It's so severe that it acts as a de facto ResetButton on the civilization of the planet.]]
* EternalRecurrence: The Great Year and it's great winter which always plunges humanity back into the stone age.
* FantasticRacism: Between the humans and phagors; both war with and enslave each other every chance they get.
* HorseOfADifferentColor: The "hoxneys", which resemble colorful zebras.
* HumanAliens: The humans of the series. Described in nearly every way as human, yet they apparently are native to Helliconia.
* HumanSubspecies: Several. Tend to be [[ButtMonkey treated horrible by both humans and phagors]]. One example is the "Madi", hobbit-like creatures with 8 fingers on each hand and "keen eyesight" -- they're most commonly depicted as slaves.
* HumanoidAliens: Phagors, the other intelligent species on Helliconia. Look like a cross between a yeti and a minotaur.
* ImportedAlienPhlebotinum: At the start of the second book, a dead man washes ashore a distant beach with a digital watch hidden on his person.
* InstantIceJustAddCold: An important plot point in the first novel, when a woman believed to be a sorceress seemingly flash-freezes a group of charging phagors. [[spoiler: The phagors charged through a pond; turns out the water was just on the verge of freezing anyway[[]] and the "sorceress" just got lucky]]
* LostTechnology: Due to the cyclical nature of civilization, the humans of Helliconia, despite starting in some cases at a near-stone age level, possess numerous devices that are much more advanced than they are capable of manufacturing, such as fine clocks or telescopes.
* MaybeMagicMaybeMundane: The human "gossies" and "fessups"; ancestral spirits seemingly able to be contacted by entering a trance. The Earth humans using long distance empathy on Helliconia. Despite these two possibly supernatural elements, the rest of the series is firmly in the "mundane" category.
** The "air octaves" and "land octaves" often mentioned in the books are used for various seemingly supernatural abilities, and yet are described suspiciously similar to magnetic fields.
* MundaneDogmatic: Despite being set on an alien world, the series reads more like a Fantasy novel (just without magic) due to the primitiveness of the human society and the novel's focus on the characters.
* ThePlague: Strikes cyclically, twice every Great Year (early in the spring and then in late fall). The first, "[[NamesToRunAwayFromReallyFast Bone Fever]]", kills half of who it afflicts, and those that survive lose at least a third of their body weight (and keep it off, as anorexia is a permanent side-effect). The second is correspondingly called "The Fat Death", which makes you gorge on anything edible, including your fellow persons, again killing about half of its victims.
** Actually the virus that induces these plagues is symbiotic with Helliconia's humans; they couldn't survive there otherwise. Only very fat people can get through the long, bitter winter and only skinny ones can survive the blistering summer.
** The virus is also lethal to non-Helliconians (i.e. Earthlings)
* PlanetaryRomance
* {{Precursors}}: Humans themselves. Humanity goes through the cycles as the "great years" pass, emerging from ignorance, building up, becoming relatively advanced, then falling back into war, ignorance, and eventually pitifulness again when the great winter falls. Cities rise up in the same location where they once were, since the ruins from past cycles are still standing (or at least the foundations provide an outline).
* ProlongedPrologue: In the first novel, the lengthy opening details the life and times of Yuli, a man who goes on to found the village where the plot takes place. The plot itself actually starts 5 generations afterward, and has nothing to do with Yuli.
* SmallSecludedWorld: Some maggots are mentioned which live in nuts, and people in-story think that the maggots must be very surprised when someone eats the nut, and the maggots suddenly realize (if they could think) that the world is much bigger than they thought. Yuli, protagonist of the prologue, compares his companions who spent their whole life in a cave to the maggots.
* WeWillUseWikiWordsInTheFuture: Summer has WikiWord names. The story is set in Earth's future, although the cultures on Helliconia have only reached the equivalent of Renaissance.