Why are there no female Space Marines?

Have come across some theories which range from the models not being up to scratch, to lore that Space Marines are almost not human, but none of these give a definitive answer.

There are female Imperial guardsmen and there are Sisters of Battle (one of the reasons the sculptures not being up to scratch is a terrible argument).

Anyone have any ideas?

  • 3
    The space wolfs books which detail the rise of Ragnar shwo the recruitment process
    – Marriott81
    Commented Mar 20, 2014 at 12:38
  • 1
    Could it also be related to the fact that there are no women in the Royal Marines?
    – Moogle
    Commented Mar 20, 2014 at 13:02
  • 7
    Possible: the gene seed used to alter them is derived from the all-male primarchs and is thus incompatible with female genes?
    – AncientSwordRage
    Commented Mar 20, 2014 at 14:11
  • 4
    Maybe there are women recruited, but after being altered to become a Space Marine they look just like men. Similar to the Borg.
    – Xantec
    Commented Mar 20, 2014 at 16:00
  • 3
    @Marriott81: to clarify: Royal Marines = the UK marine corps, and Games Workshop, the company that makes WH40K is a UK company. Commented Mar 21, 2014 at 11:34

11 Answers 11


The in-universe answers I have seen are twofold:

Firstly the Primarchs were all male; space marines are created using their gene seed and it reacts poorly to being implanted into a female.

As others have pointed out, from Lexicanum we have:

They must be male because the zygotes are keyed to male hormones and tissue types.

Secondly (and possibly most importantly) the Imperium of Man is a place where tradition and ritual are treated as important above all other things. Space marines were male when the Emperor created them, so they will ALWAYS be male. To even think otherwise is heresy.

From an out-of-universe perspective; Games Workshop first created the Space Marines in the 80s to appeal to 13 year old boys. Back then the idea of girl space army men was probably not in vogue.

  • 9
    it reacts poorly to being implanted into a female : This sounds like you've seen examples. Is there a source for the positive assertion? +1 for the tradition though.
    – Xantec
    Commented Mar 20, 2014 at 16:19
  • @Xantec Somewhere, I think maybe an old issue of White Dwarf.
    – evilscary
    Commented Mar 20, 2014 at 16:19
  • But what if a space marine initiate identifies as male?
    – WOPR
    Commented Mar 7, 2019 at 23:55
  • 4
    Simples answer could be - "If it was easy and possible, Chaos Legions would do it". Chaos does have his own scientist like infamous Fabious Bile, who managed to clone Horus and currently attempts to clone the Emperor.
    – Yasskier
    Commented Jun 13, 2019 at 22:00

The Imperium has actually lost the technology required to create new gene-seed, especially on the level of a Primarch. Many people have tried, but have failed. The closest that anyone got to creating new gene-seed was actually the Space Wolves, but Magnus attacked Fenris and destroyed the research lab there - forever keeping the Space Wolves from creating any successor chapters. They made one before, but that chapter was corrupted by Magnus himself.

The Emperor did know of Alpharius Omegon, remember that he created both of them. It may have not been planned for the embryo to split, but that's what it did and it had to have happened before Chaos threw the Primarch's across the galaxy. So, the Emperor was aware of the twins but kept it secret for unknown reasons. I believe in one of the books in the Horus Trilogy it briefly discusses when the Emperor found the Primarchs and knew them both to be twins.

Woman would not be ideal candidates to be Space Marines for several reasons.

  1. Most male neophytes die during the organ plantation. You need physically fit candidates, and one's that have strong bodies at a younger age. Young girls would die right out from the procedures.
  2. The Primarch's gene-seed would not be compatible with the genes of a girl, and the two different genes would destroy each other. Killing the host.
  3. Space Marines are an icon in the Imperium, a woman could never be seen as such. The Emperor created the Space Marines from men, thus they will stay as men - even though it's impossible for women to actually become a Space Marine.

The closest you'll get to female Space Marines are the Sisters of Battle.


The Adeptus Astartes are the Space Marines, and are (so far as I know) all male.

But don't despair for the women, they are not left out of the never-ending war. The Adepta Sororitas or Sisters of Battle is the women's division of the forces of the Emperor. The Sisters tend to operate more as an arm of the Inquisition than in "traditional" theatres of operation. Check the wikia link for more in-depth information on this chapter.

I also like the comment @Pureferret has that the geneseeds for the Adeptus Astartes are taken from the Primarchs and thus are inherently male DNA, and thus may be incompatible. I'm no biologist, but this does sound like it makes some sense too.

  • 3
    I know that the reason is that the SOB order is not allowed Men at Arms which is why they are all female, but I was curious about the Smurfs and the like
    – Marriott81
    Commented Mar 21, 2014 at 16:13
  • 3
    The original Rogue Trader included a John Blanche picture of an Adepta Sororitas (whose power armour definitely featured, thank you Pterry, a breastplate) and a short paragraph about them being the most fervent followers of the Emperor. So from the first days of the game, the Astartes were conceived of as all-male and the Sororitas as all-female. The Imperial Guard OTOH were always inclusive of both, and the first metal Guardsman miniatures included a number of Guardswomen. The plastic Guard miniatures were all guys though.
    – Graham
    Commented Feb 13, 2020 at 12:51

Another way to think about it is that the gene-science used to create the Primarchs and marines was exceptionally difficult. Neither the Emperor nor a similar powerbroker ever succeeds in replicating the same Primarch -> Geneseed relationship again.

Given how precarious the geneseed mutations of male candidates were found to be, it stands to reason that there simply was not enough expertise to then also create a similar process for female marines. Even before the Heresy it's well known among the Primarchs, Malcador and the Emperor that several legions possess unstable geneseeds. It's even hinted that at least one of the two lost legions suffered the fate of expungement due to faulty geneseed. Hence, a process as finicky, and frankly error-prone, as the creation of a space marine probably never gets to the point where the powers that be consider expanding to female subjects.

Also note that the Emperor's Custodians are also all male. It could simply be that the gene enhancement techniques developed during Terran unification focused only on male physiology too. There was not a need for more warriors so much as an efficient and trusted cadre of super-human ones, the Adeptus Custodes. If so, again the need for investing research and development into female enrollment is not needed when a small number of elite male warriors would suffice.


Just to help with this all of the gene-seed was originally crafted in the 30th Millennium by the Emperor of Mankind in his Himalayan gene-laboratories deep beneath the Himalayan Mountains for this purpose using the genomes of each of the 20 Primarchs as a template. (Here is a little real science for you) In May of 2017 an article was published that "out of 20,000 genes looked into 6,500 of them are expressed differently in men and women." So that is more than 25 %. (back to the game) Since the First Founding, the Chapters of the Adeptus Astartes have lost the ability to engineer new gene-seed or implant organs from scratch. Now using the gene-seeds they are stuck with some chapters are lucky to have a 1 in 10 success rate other 1 in 100 and that is with males who's genomes are most likely to be compatible with the original gene seeds.

So there you have it even if you just did it on the math alone the ones that have a 1 in 10 using males(10% success) would be lucky to get a 3 in 40 using females(7.5%) and the ones with 1 in 100(1% success) would be lucky to get a 3 in 400(0.75%) using females so from a pure math position you go with the highest success rate. Not to mention if you go from a science stand point of the 6.5 K genomes that are different between males and females how much do you want to bet that there aren't a good chunk of those that are inherently different in the genders that are required to make it work so now you drop the success rate from 3 in 40 (7.5 %) success rate to 0.00000000000000000000000000000000001 % success rate or 1 out of 10000000000000000000000000000000000 because you will have that one freak of nature that is a female but possesses all of the required missing male genomes in there body as a mutation.

Sorry to say it but men and women are not identical that is why some medicine works better for women than men and vice versa, same for ethnicity, it is no one trying to be mean except maybe mother nature. So until someone succeeds in replicating the lost technology sorry it is not going to happen and it is still not going to happen because the Emperor (may his will guide my words) based his research off of the aborted Primarch project.

Now the Primarch project led to the creation of the Primarchs who were the twenty genetically-engineered "sons" of the Emperor of Mankind, and the genetic "fathers" of the Space Marine Legions. The Emperor used his own DNA in their creation. It is said they were created with the Emperor with the aid of forbidden sciences and arcane lore derived from the Warp. The Emperor utilized dark powers to construct the Primarchs. It is speculated the Primarchs were imbued with energies and knowledge that the Emperor gained in a Warp Portal on Molech.

So in order to rediscover the technology you will have to uncover the forbidden sciences and arcane lore in the warp which is deadlier now in 40 K than it was in 30 K, do this without the Emperors help of course because he is in no condition to go there, return back and get DNA from the Emperor which should be fun if any of it is still viable and you can get to the golden throne, genetically alter his DNA to give birth to a Female Primarch without corrupting it. Then use the genome of that Primarch to create new Gene Seeds, which by the way is also lost technology and needs to be rediscover then you can make a female space marine. Have fun. By the way the above is only about a 10th of what would have to be done if that. There was a lot more to making the Primarch's alone than what I have above the, the lore in Warhammer is so in-depth it makes real life seem simple so it takes quite a bit to alter Canon lore without alienating your current ensured fan base to such a degree that you lose all of them for an unknown fan base you may possibly gain but are not assured to gain.

  • This appears to be a good answer, but it's a bit hard to follow. A summary paragraph explaining why there aren't female Marine's might help. Welcome to the site!
    – JohnP
    Commented Apr 27, 2018 at 15:38
  • This is making my brain hurt. The Doylist answer suffices. Please explain how you conclude that half the species is "missing" thousands of "genomes".
    – swbarnes2
    Commented Apr 27, 2018 at 21:17

well it would seem to the average lore follower that all the Primarchs were male, however, upon closer inspection of the history of the ultra marines, there is a segment that many of the lore followers overlooked. the two lost Primarch's, whose statues were eventually removed from the palace on terra were never really discussed in the series by the loyalists, but instead were mentioned by the horus traitors. it's important to note that gender was not mentioned for these two primarchs, secondly the primarch of the alpha legion had a twin that emperor didn't even know about! so there was a slim chance of the two being females?= female space marine gene seed? however, because horus mentioned them at all, it's a safe bet that they were already killed off by the forces of chaos, but what's stopping the imperium of man from creating a new set of female primarchs, or even just one, so that even the lowly female guardsman could become a space marine. and wage all out war against the enemies of the empire?

  • 2
    Welcome to scifi.stackexchange. It looks like your answer could have something useful in it, but in its current format it is hard to understand. You might want to edit it to make your point more clear.
    – numaroth
    Commented Oct 1, 2014 at 20:25
  • I like the idea of the two redacted Primarchs being female, with legions of female space marines. I think this makes the taboo around them even more interesting - the Primarchs killed their only two sisters.
    – Falco
    Commented Nov 3, 2022 at 14:15

Because of how they were engineered only men can accept the gene-seed of the male Primarchs. If there were female Primarchs this would have been possible, but because they do not exist this is not possible.

Do note that in one of the recent Horus Heresy novels Malcador the Sigilite mentioned to Rogal Dorn that he once advised the Emperor to make some of the Primarchs female because they would lack the rivalries and proneness to infighting common amongst brothers, and that some sisters thrown into the mix would lessen this risk. Rogal Dorn was not amused by this, and even His Imperial Majesty was royally flabbergaste that Malcador suggested this with a straight face.


What is known of Space Marines gene-seed transformation are the following:

  • the Emperor, whether lying or truthful, states that only men can be Space Marines; so, while this does include transwomen, it does not include women or intersex people;
  • whatever the circumstance, scientific progress by the scientific method and empiricism would be deemed heretical due the Imperium/Mechanicus's obsession with STC technology; so, if one wants to mess around with the Emperor's line of experiments, it would have to be done very discreetly, which would still probably be noticed by Inquisition, so the only way around that is to be part of the Inquisition. Or you could try to take deep into Mars in the old parts of the Tech-Priest civilization, which also comes with its own problems.

As Space Marines, Thunder Warriors, and Custodes are not all the same thing, and the Emperor specifically was talking about Space Marines, then it can be assumed that Thunder Warriors and Custodes (the most powerful of the three), can include women and intersex people.

It should be noted this is quite literally the only thing women can't do in the Imperium. They can join any other branch of the military and attain any government or order position or anything in the professional world besides being a Space Marine and all humans of the Imperium are citizens holding equal rights.

This is assuming of course that aspect of Imperial law, of equality, is actually enforced throughout all the planets of the Imperium, but I suspect that where the Adeptus Sororitas,the Adeptus Mechanicus and the better groups of the Imperial Guard, Knights, Ordo Tempestus, Imperial Navy, Adeptus Astartes and the Arbites are, it'll be enforced. I put the Tech-Priests up there because they would find sex and gender equality illogical, so they have that to be thanked for despite their other shortcomings in human right.

  • 2
    "and all humans of the Imperium are citizens holding equal rights." Hahahahahahahaha.
    – Adamant
    Commented Jun 4, 2022 at 17:50

The nature of gene seed aside, It has to do with logistics and statistics. There are roughly 1 million space marines at the time of the 41st millennium, roughly one marine for each planet in the Imperium. Assuming the average planets has the same population as earth today, that means that there's 1 space marine for roughly every 7 billion mortal humans. Now when it comes to picking recruits to become space marines, that means that in order to be selected, you have to be the strongest, fastest, biggest human out of 7 billion humans, and that person is always going to be a man, without fail. Hell, even out of a group of 100 humans, 50 men and 50 women, the strongest person in that group of 100 is going to be a man virtually every time. Even if Gene seed were compatible with female anatomy, no female recruit would ever be able to compete against the male recruits at such a staggeringly high level of physical performance and human ability.

Tldr: in order to even be considered for recruitment into the astartes, a person has to be the strongest human out of a group of (at least) 7 billion humans (reflecting the ratio of space marines to mortal humans), and that person is always going to be a man.

  • And you have evidence that this holds true 38 000 years from now? Heck, do you have evidence it's true categorically today?
    – DavidW
    Commented Jun 24, 2022 at 18:56
  • @DavidW: who knows about 38k years from now, but I don’t think anyone disputes this today. Take a look at the top powerlifting records for men vs women…it isn’t even close. Or this study on grip strength, a good proxy for overall strength. link.springer.com/article/10.1007/s00421-006-0351-1
    – Shamshiel
    Commented Jun 24, 2022 at 21:54

There are currently no known female Space Marines, mainly due to the genetic problems mentioned by others. That being said, the possibility of that changing some point in the future has opened up a bit with the introduction of Primaris Space Marines. The reason I think this is that, if the gene seed can be manipulated to make primaris marines, it could possibly be altered further in the future.


Well the gene problem only explain why since all primarch are male space marine are male.. By the way "creating" a space marine does include base upgrade but the entire process is centered around transforming the aspirant into something reassembling the primarch. That why the sons of horus ressemble him à lot, why most thousands sons are psyker and why the blood angel can still feel the death of their primarch. So in all that technicality we aren't talking about WHY all the primarch are men. Because, in my opinion, primarch where made by the Emperor "in his image" using his gene and each represent a part of the emperor. An aspect of his human psyche. The ultramarine being his pride, the lunar wolves his ambition the thousands sons his desire for knowledge and power The space wolve being his animalistic nature ect ect The primarch are more of a deformed copy of himself than of a real sons. That is a reason why he never really treat them as sons, why he has complete confiance but also don't estimate them much.

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