This is really getting to me. Two points I know of.

Dogmeat is modeled after River, a female German Shepherd, owned by Michelle Burgess who is the wife of http://fallout.wikia.com/wiki/Joel_Burgess, Senior Designer at Bethesda Softworks.http://fallout.wikia.com/wiki/Dogmeat_%28Fallout_4%29#cite_note-3

So that suggests female.

However the SS refers to Dogmeat as “Boy” which suggest male, but maybe “Boy” is used in an asixual way?

I would find ether convincing, both together completely confusing. So anything else?

Dogmeat has always been a male dog.

They don't model the bits because people tend to be weirded out by that sort of thing.

Hes always been a male

Dogs in Fallout have always been male.

Why? Who says?

Still very confused, spieces should be extinct by now unless dogs are ghouls as well or somone is purposly breeding only male dogs?

If you model somone on a girl, its natural to assume they are a girl. Very strange.

Dogmeat is Dogmeat, semi-mythic demigod franchise figure who appears to the protagonist in times of need.

A person? Duh. A dog? Don't have any distinguishable features between male and female aside from genitals.

Its a male, but yes its modeled after a [censored]. hihi, not often i can use that word without beeing slapped afterwards.

I wish we could rename him. You know something cool like Fido, Rin-Tin-Tin or the classic Dog

Actually, the game just calls him "Dog", which is probably better than Aardvark or Wombat, but not nearly as cool as Fang, Fleabag or Kibblehund.

It'd be cool if we could name him.

I'd rather have a cat....

Ok so as I see it, the reasons for believing Dogmeat is male are.

The SS refers to him as "Boy".

Dogs in previous Fallout games have been male. (Not sure why that is relevant?)

Confident assertions from random people for unspecified reasons.

Reasons for believing Dogmeat is female.

He is modelled on a female dog.

Dogmeat is neither male or female. Dogmeat is awesome.

If you don't think awesome can be a six then I am saddened by your lack of experience.

(That was a joke)

The Doctor: Male? Female? Awesome!

Dovahkiin: Awesome!

Captain Jack Sparrow: Awesome!

Captain Jack Harkness: Awesomesixual...Oh my!

Watch the "red rocket" episode of south park and look at red rocket gas station you meet dogmeat at and than ask if he is a boy or not.

'Meat is definitely male GSD by default of the name alone

As an OT:

As much as I love DM, it never ceases to baffle me in what a pristine pre-war condition your PC finds him. Did he find a way to shield himself from the rads by eating all that canned prewar dog food my PC keeps finding around the wasteland?? How is it @#$!%!?# even remotely possible for DM to look the way he does, given the 1/2 ghoulish look that ALL the other canines (Raider domesticated or feral) do in the wasteland?

Basically, how the heck did DM ever escape being irradiated?? How did the Fallout rad effects miss hitting up his gene pool so completely? <--could it be possible the rad fallout ended up removing his family jewels??

This leads me to the conspiracy theory that Vault 111 might have also cryogenically preserved dogs besides ppl. And dogs and dogs alone. Because despite the archaeological evidence of several plastic pre war pet bowls in the Commonwealth, there are ZERO mutated felines some 200 years later. And no, don't tell me their descendants got eaten by a Yao Gui or pack of DM's hillbilly feral cousins.

Same goes for the complete lack of pet budgies/canaries/parrots ANYWHERE in the wasteland. Americans must have really, really hated having cats and pet parrots......

Find a working copy of Fallout 2 and target a dog's crotch. What I posted was the successful hit message.

I still don't understand why a dog in Fallout 2 being male means Dogmeat must be?

BTW for conspiracy theorists there is a third option, that Dogmeat is a synth. So to what extent do syths have sixes?