The codex astartes specifies that a chapter should have 10 companies, each of the first 9 have 100 marines. The 10th company is the scouts company and has no formal limit.

Not all chapters follow the codex strictly with the Black Templar and Space Wolves in particular springing to mind.

Which chapter that is still loyal to the Imperium has the largest membership?

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    Currently? As of August 2018?
    – user14111
    Aug 8, 2018 at 23:58
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    @user14111 I think the charitable reading of that is as of the release of 8th Edition and the ensuing advance of the timeline.
    – Fomite
    Aug 9, 2018 at 4:51

3 Answers 3


Black Templars

They exact numbers are unknown, but believed to be over 6000 Marines (six times above the limit).

It is said that only the High Marshal has any idea of the Black Templars' full numbers, but it is rumoured in the Inquisition that they actually number close to 6,000 Space Marines. That would make them nearly as large as some of the original First Founding Space Marine Legions after the terrible losses of the Horus Heresy, and means that the Black Templars are one of only three Chapters of Astartes (the others being the Space Wolves and the Grey Knights) thought to violate the 1,000 Space Marines to a Chapter limitation as proscribed by the Codex Astartes.

The Black Templars not as much ignore the Codex Astartes (as Space Wolves do), but rather found a loophole: in the Codex, each chapter was allowed to gather additional numbers, whenever they were participating in a crusade. Sigismund looked at that and declared, that Black Templars are ALWAYS on a crusade so they are following the law to the letter.

Lords of Terra and Inquisition are mostly fine with that, since the Templar forces are scattered across the galaxy.

Another possible contender (although you couldn't call it a chapter) is the


Unlike other Space Marines, the ones serving in the Deathwatch are not truly a separate Chapter of the Adeptus Astartes; rather, they are a collection of Veteran Space Marines drawn from all of the different extant Chapters who serve together in the Inquisition's service for a discrete period of time.

Their numbers are unknown and vary from time to time, but it is believed to be slightly below 5000.

Finally, similarly without exact known numbers is the


Similar to the Deathwatch, they are not a single chapter but a group of warbands of marines that abandoned their original chapter (or... legion!) and decided to seek redemption in the eyes of the Emperor. Originally Blackshield warbands were created after the Horus Heresy from the leftover loyalists from the Traitor legions. An individual Blackshield warband can count from few marines to well over 2000 and no one really knows, how many such warbands exist.

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    I'd be highly skeptical that Blackshield warbands of any size that are still nominally independent exist in any real size. They show up in the Deathwatch codex (we think - the name is the same at least) as individuals.
    – Fomite
    Aug 9, 2018 at 4:52

I don't think there's any published record of this. A few credible guesses:

  • The Black Templars: As noted, they've essentially ignored the codex entirely and carried on with this whole Great Crusade concept. With the size of the fleet they have, how broken up they are, and Dorn's clear hesitance to break up his legion, it's quite possible they are well above standard Chapter strength.
  • The Dark Angels: In their later fluff, it's clear that the Unforgiven are following the letter of the law, rather than the intent, regarding Chapters. So while each individual "Chapter" might be at standard strength, if they're all hanging out on the same space fortress, following the same commands...are they really separate?

The Space Wolves would be another contender, but given how hard they've been hit with the attack on Fenris and the Fall of Cadia, my guess is right now they're badly understrength. They were also a small Legion to begin with, and were badly depleted after the Heresy.

  • Just like those sneaky Dark Angels, the Imperial Fists and successors also have the Last Wall protocol, though that's not technically one chapter, it does bring them all together under one learder
    – TommyBs
    Aug 9, 2018 at 8:09

i would say the dark angels, every supposed succesor chapter of them is founded to bring something to the fight the entire legion needs, along with that every chapter master of the 'successors' is inducted into the legions inner circle that follows the orders of the chapter master of the dark angels. they arent a chapter, they are a legion.

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