What Is Warhammer 40K? A Beginner's Guide

The full sacred record. Written to be read, not consulted.

Warhammer 40,000 is a setting built on a single, load-bearing catastrophe, and understanding it is the fastest way to understand everything else. It is Games Workshop's science-fiction universe — first published in 1987 as a tabletop miniatures wargame and grown, over the decades, into one of the largest science-fiction settings ever created, spanning hundreds of novels, dozens of video games, and a worldwide hobby. Its premise is simple and bleak: it is the 41st millennium, roughly thirty-eight thousand years from now, and the galaxy is a place of unending war. There are no good times coming. As the setting's famous tagline puts it, "in the grim darkness of the far future, there is only war."

That single line does a great deal of work. Warhammer 40,000 is not a story about heroes saving the day. It is a story about survival at any cost, about a humanity that has become the very thing it once feared, and about a galaxy so vast and so old that hope itself has come to look like a kind of heresy. But before we reach the war, it helps to understand what 40K actually is — because it is two things at once.

More than a story: the hobby

At its foundation, Warhammer 40,000 is a tabletop miniatures wargame. Two or more players assemble armies of small, highly detailed plastic models — from lone characters to towering war-machines — and fight battles across a tabletop using dice, tape measures, scenery, and a shared rulebook. One player might field a disciplined strike force of Space Marines; another a green tide of Orks, a swarm of Tyranids, or a phalanx of soulless Necrons. The rules decide who shoots, who charges, and who is left standing when the dust settles. Games can be quick skirmishes or vast, campaign-spanning wars, and the setting's factions are deliberately distinct so that each one plays and feels different.

But the game is only half of it. The other half is the craft: collecting the miniatures, assembling them, and painting them. For a huge number of fans, the hobby is the painting — the quiet, absorbing work of turning a bare grey model into something that looks like it stepped straight out of the artwork. You do not even have to play to enjoy 40K; plenty of people simply build and paint, or read the novels, or follow the lore from the outside. The game has been revised through a series of new editions over the years, each one refreshing the rules, but the core loop — collect, build, paint, play — has stayed the same since the very beginning. For newcomers, the usual entry point is a starter set, which bundles two small armies, the rules, dice, and everything needed to play a first game.

Underneath that hobby sits the reason it has endured for nearly four decades: the setting. And the setting begins, as everything in 40K does, with the past.

The Emperor and the Great Crusade

To understand the present, you have to start ten thousand years before it. In the 30th millennium a being known only as the Emperor of Mankind — a near-immortal, immensely powerful psyker who had guided humanity from the shadows for millennia — revealed himself and set out to reunite a scattered, war-torn human species under one rule. This was the Great Crusade: a campaign to reconquer the galaxy for humanity, to end superstition and fear, and to build a rational, secular empire lit by science and reason. It was, by design, a hopeful project — perhaps the only genuinely hopeful chapter in the whole setting.

To lead his armies the Emperor created the Primarchs — twenty transhuman sons, engineered to be generals, demigods, and the pinnacle of human potential. From their genetic material he built the Space Marines, the Adeptus Astartes: superhuman warriors encased in power armour who remain the setting's iconic figures to this day. For a brief, shining moment, it worked. World after world was brought back into the fold; the darkness was pushed back; and the dream of a united humanity seemed within reach. That it did not last is the entire point of Warhammer 40,000.

The Horus Heresy: the betrayal that defines everything

Then it all came apart. The Emperor's favoured son and appointed Warmaster, Horus, fell to the corrupting influence of Chaos and turned half the Primarchs against their father. The resulting civil war — the Horus Heresy — is the single event that every other story in 40K leans on. Brother fought brother across the galaxy. At the Drop Site Massacre on Isstvan V, entire loyal legions were annihilated by treachery. The war climbed toward a desperate, apocalyptic siege of Terra itself, humanity's homeworld, where the Emperor finally struck down his rebel son in single combat — but was mortally wounded in the doing of it.

The Emperor's broken body was interred upon the Golden Throne, a vast and half-understood arcane machine that keeps him alive but silent, suspended forever between life and death. The surviving traitor legions fled into the Eye of Terror, a great wound in reality where the material universe and the hell-dimension of Chaos bleed together. The rational, hopeful empire the Emperor had tried to build died with his defeat. What rose in its place was something far darker — and far more enduring: the Imperium of the 41st millennium.

The Imperium of the 41st millennium

The Imperium of Man is humanity's galaxy-spanning empire, and it is a nightmare of its own making. It spans a million worlds and untold trillions of people, but it is brutal, paranoid, stagnant, and drowning in its own bureaucracy and dogma. The Emperor who explicitly forbade his own worship is now venerated as a literal god, the still centre of a vast and merciless state religion. To question that faith is heresy, punishable by death. Ignorance is treated as a virtue, curiosity as a danger, and the mere suspicion of difference — a mutation, an unsanctioned thought, contact with aliens — can damn an entire world.

This empire is held together by a sprawling cast of institutions, each vast enough to be a setting in its own right. The tech-priests of the Adeptus Mechanicus worship machines as sacred and hoard technology that no one fully understands anymore, wringing survival from relics they can barely repair. The endless conscript armies of the Astra Militarum — the Imperial Guard — hold the line in their untold billions, ordinary humans thrown against horrors far beyond them. The zealous Adepta Sororitas, the Sisters of Battle, carry the fire of the faith into war. And the secretive, all-powerful Inquisition hunts heresy, mutation, and alien influence with absolute authority and no mercy at all, answerable to no one but itself. It is not a good place to live. But it is humanity's only bulwark against things far worse.

The Warp: the engine of the setting

Almost nothing in Warhammer 40,000 makes sense without the Warp. Also called the Immaterium or the empyrean, the Warp is a parallel dimension of pure psychic energy that underlies the material universe — a roiling ocean of raw emotion, memory, and nightmare. It is, for all practical purposes, hell. It is the home of the Chaos Gods and their daemons, and it is shaped by the feelings of every living creature in the galaxy: every act of rage, despair, hope, and desire ripples out into it and feeds the powers that dwell there.

The Warp is also completely indispensable, which is the setting's cruel joke. Faster-than-light travel is only possible by plunging ships into the Warp and riding its violent currents — a journey so perilous that vessels depend on mutant Navigators to steer and on the Astronomican, a colossal psychic beacon powered by the Emperor and fuelled by the daily sacrifice of a thousand psykers, to find their way through the dark. Psykers — humans born with the power to channel the Warp — are at once the Imperium's most valuable weapon and its deadliest liability, because an untrained or unlucky psyker is a doorway through which daemons can pour into the material world. To use the Warp is to court damnation, and the Imperium has no choice but to use it every single day.

The enemies of Mankind

The Imperium survives only because it never stops fighting, because its enemies are everywhere and relentless:

Chaos — the four dark gods of the Warp (Khorne, god of war; Tzeentch, of scheming and change; Nurgle, of decay; and Slaanesh, of excess) and the traitors, cultists, and daemons who serve them. Chaos is the setting's central threat: it promises power and delivers damnation, and it feeds on the emotions of every living thing.
The Aeldari — an ancient, dying elder race, spiritually magnificent and terribly arrogant, whose own hubris and excess birthed the Chaos god Slaanesh and shattered their once-galaxy-spanning empire in a single night.
The Drukhari — the Aeldari's sadistic dark kin, piratical raiders from a hidden city who sustain their immortality by inflicting suffering on captives dragged back from a thousand worlds.
The Orks — a fungal, endlessly warlike species who genuinely love fighting for its own sake, breed without limit, and whose sheer collective belief can bend reality to make their crude weapons work.
The Necrons — soulless robotic legions who slept for sixty million years in tomb-worlds beneath the galaxy's surface and are now waking, dynasty by dynasty, to reclaim a domain that predates humanity itself.
The Tyranids — an extragalactic swarm of bio-engineered horrors driven by a single vast Hive Mind, devouring entire worlds and star systems to fuel their advance, and answered on the ground by hidden Genestealer Cults that rot worlds from within.
The T'au — a young, idealistic, technologically advanced species expanding under the banner of the "Greater Good," and one of the very few factions in the setting with any real optimism left.
Itself — and never forget that the Imperium is cruel, corrupt, riven by internal politics, and frequently its own worst enemy.

The present day: a galaxy torn in half

The "present" of the setting is not static — the story has moved forward, and dramatically so. After ten thousand years of grinding stalemate, the Imperium's ancient fortress-world of Cadia finally fell to the forces of Chaos, and in the aftermath a cataclysmic warp storm called the Great Rift (the Cicatrix Maledictum) tore across the galaxy from end to end. It plunged half of the Imperium into darkness and cut it off entirely from the light of the Astronomican, stranding countless worlds in a new dark age of daemon-haunted night.

And then, in humanity's darkest hour, something almost unthinkable happened: hope. One of the loyal Primarchs — Roboute Guilliman, lord of the Ultramarines — was resurrected after ten thousand years in stasis, returning to a galaxy that had made a god of his father and a ruin of his father's dream. Horrified by what the Imperium had become but bound to defend it, Guilliman now leads a desperate counter-crusade, the Indomitus Crusade, to hold the crumbling empire together — reinforced by a new and more powerful generation of Space Marines, the Primaris, engineered over long centuries to turn the tide. Whether they can is, deliberately, an open question. In 40K, even the return of a demigod only buys time.

Beyond the tabletop

Warhammer 40,000 long ago outgrew the tabletop. Its fiction is published by Black Library, Games Workshop's in-house imprint, which has released hundreds of novels and short stories — from the sprawling Horus Heresy series that dramatises the great betrayal in full, to character-driven sagas that have become beloved in their own right. For a great many fans, the books are the real doorway into the setting, the place where its grim mythology comes alive.

It has also become a major presence in video games, most famously the hard-hitting Space Marine action series, alongside strategy games and titles across nearly every genre. And the setting is now reaching the screen: a live-action television adaptation is in active development, a sign of just how far 40K has travelled from a single box of miniatures in 1987. Whatever door you come through — a starter set, a novel, a video game, or one arresting piece of artwork — they all lead back to the same enormous, terrible, magnificent galaxy.

Why Warhammer 40,000 endures

What makes 40K last is that its bleakness is rendered with real craft and, very often, real feeling. This tone has a name that fans use constantly — grimdark — and it is entirely deliberate. There are no clean heroes here, only degrees of desperation, and that is exactly what gives the setting its strange gravity. Across thousands of novels and codexes, behind a facade of gothic excess and impossibly large guns, 40K keeps asking genuine questions about faith, sacrifice, loyalty, and what survival is actually worth. It is satirical and sincere at the same time, a warning and a wonder. You can enjoy it purely for the spectacle of ten-foot warriors fighting daemons, or you can go looking for the tragedy underneath — and it rewards both, which is precisely why people fall in and never quite climb back out.

If you want the origin of it all, read the Horus Heresy — the betrayal every other story leans on. If you want to start with its most famous soldiers, read what the Space Marines are. If the corruption is what draws you, read what Chaos is. And when you are ready to actually begin, here is how to get into 40K.

Warhammer 40,000 — usually shortened to "40K" — is Games Workshop's science-fiction setting, and the most popular corner of the wider Warhammer universe. It began in 1987 as a tabletop miniatures wargame, where players field armies of small plastic models and fight battles with dice, rules, and terrain — but the hobby is as much about collecting, building, and painting those models as it is about playing. It has since expanded into an enormous body of novels, video games, and lore, but at its heart it is still a story about a galaxy at war.

The setting takes place in the 41st millennium, a future so distant and so ruined that its own history has become myth. Humanity is united — barely — under the Imperium of Man, a vast, brutal, superstitious empire spanning a million worlds. It is ruled in the name of the Emperor, a near-immortal being who has spent the last ten thousand years interred on the Golden Throne, kept alive but silent, worshipped as a god he never wished to be. His empire is stagnant and cruel, ruled by fear and faith, and it is slowly losing.

The Imperium survives because it never stops fighting. Its enemies are everywhere:

Chaos — the daemonic gods of the Warp and the traitors who serve them, the setting's central threat.
Xenos — alien civilisations: the savage Orks, the ancient Aeldari, the machine-undead Necrons, the devouring Tyranids, the idealistic T'au, and more.
Itself — the Imperium is cruel, paranoid, and often its own worst enemy.

Almost everything wrong with the setting traces back to one event: the Horus Heresy, a galaxy-spanning civil war ten thousand years ago in which the Emperor's favoured son betrayed him and half of humanity's greatest warriors turned traitor. The Emperor won, but was mortally wounded, and the hopeful empire he had been building died with his defeat. What survived hardened into the grim theocracy that rules today.

The tone is the famous "grimdark": there are no clean heroes, only degrees of desperation. That is deliberate, and it is why 40K reads more like tragic mythology than space adventure. This is the setting most newcomers mean when they say "Warhammer," and it is the easiest to fall into — whether you come for the models, the video games, or the books.

Warhammer 40,000 — "40K" — is Games Workshop's science-fiction setting and tabletop miniatures hobby: a galaxy roughly 38,000 years from now where a dying human empire wages endless war against aliens, daemons, and itself. It is the darkest, largest, and most popular corner of the Warhammer universe, home to the Space Marines, the God-Emperor of Mankind, and the ruinous powers of Chaos. It began in 1987 as a wargame — players collect, build, and paint armies of models — and has since grown into novels, video games, and a major franchise. If you have seen towering armoured warriors with skulls on everything, that is 40K.