The Ultramarines are the XIII Legion of Space Marines, the blue-armoured sons of Roboute Guilliman. They’re the poster boys of Warhammer 40,000, and for good reason: their Primarch wrote the book on how a Chapter should fight, and they’ve been following it ever since.
Who they are
Originally called the War-Born, the Ultramarines were one of the twenty First Founding Legions. After the Horus Heresy, Guilliman’s Codex Astartes split the Legions into smaller Chapters, and only the foremost kept the original name.
Their homeworld is Macragge, and their fortress-monastery is the Fortress of Hera. They wear blue, white, and gold, and their current Chapter Master is Marneus Calgar. The battle cry is ‘Courage and Honour!’ or ‘We march for Macragge!’
Why they matter
Guilliman didn’t just lead them, he wrote the Codex Astartes, the tactical doctrine that defines how most Space Marine Chapters are organised and fight. That makes the Ultramarines the template every other Chapter is measured against.
They’re also one of the most powerful Imperial organisations on the Eastern Fringe. Their territory, the Realm of Ultramar, is a stellar empire in its own right, and their many successor Chapters extend their influence across the galaxy.
The Codex Astartes and how they fight
The Ultramarines follow the Codex strictly, but it’s not a rigid script. It teaches balance: they train to excel in every area of war rather than specialising like some other Legions.
One rare deviation is the Tyrannic War Veterans, a formation made up entirely of Marines who’ve survived battles against the Tyranids. It’s a practical response to a threat the Codex didn’t originally anticipate.
- Legion number: XIII
- Primarch: Roboute Guilliman
- Homeworld: Macragge
- Chapter Master: Marneus Calgar
- Specialty: combined arms, diplomacy, logistics
- Strength: roughly 1,000 Marines
History in brief
During the Great Crusade they were a mass-assault Legion, known for planetary interdiction and liberation campaigns. Then came the Horus Heresy, and the Battle of Calth, where they fought their traitor kin in one of the war’s bitterest campaigns.
After the Heresy, Guilliman wrote the Codex and broke his Legion into Chapters during the Great Scouring. The Ultramarines have been the model Codex Chapter ever since, though recent events have pulled them back toward larger-scale warfare.
How they connect to other lore
Because the Codex Astartes shaped so many Chapters, the Ultramarines sit at the centre of Space Marine identity. Their successor Chapters, sometimes called the Ultramarines’ gene-line, are among the most numerous in the Imperium.
Guilliman’s return in the modern setting has made them even more central, tying them directly to the Imperium’s current struggles and the Indomitus Crusade.
Key facts
- The Ultramarines are the XIII Legion, originally called the War-Born.
- Their Primarch is Roboute Guilliman, author of the Codex Astartes.
- Homeworld: Macragge; fortress-monastery: Fortress of Hera.
- Chapter Master: Marneus Calgar.
- They follow the Codex Astartes strictly, with rare exceptions like the Tyrannic War Veterans.
- They control the Realm of Ultramar on the Eastern Fringe.
FAQ
Who is the Ultramarines’ Primarch?
Roboute Guilliman, who wrote the Codex Astartes and later returned to lead the Imperium in the modern era.
What is the Realm of Ultramar?
It’s the stellar empire the Ultramarines control on the Eastern Fringe, made up of multiple worlds and defended by the Chapter and its successors.
Why are the Ultramarines so popular?
They’re the archetypal Space Marine Chapter, blue-armoured, disciplined, and central to the lore thanks to Guilliman and the Codex Astartes.