Forget David Cameron's much-heralded move to bring more women into the cabinet. Marvel Comics trumped No 10 on the same day by announcing that one of their most established male characters is changing sex.

Thor, who debuted in the Journey Into Mystery title in 1962, has also been the star of two movies in the latest Marvel big-screen series; plus he played a pivotal role in the Avengers cinematic adaptation.

It's hard to imagine a more masculine character than Thor, who is based on the god of thunder of Norse myth: he's the strapping, hammer-wielding son of Odin who, more often than not, sports a beard and likes nothing better than smacking frost giants.

However, Marvel says that a new series written by Jason Aaron with art by Russell Dauterman will re-cast Thor as a female character. The comic, launching in October, is billed by Marvel as "one of the most shocking and exciting changes ever to shake one of the 'big three' of Captain America, Iron Man and Thor".

Marvel editor Wil Moss said: "The inscription on Thor's hammer reads, 'Whosoever holds this hammer, if he be worthy, shall possess the power of Thor.' Well, it's time to update that inscription. The new Thor continues Marvel's proud tradition of strong female characters like Captain Marvel, Storm, Black Widow and more. And this new Thor isn't a temporary female substitute – she's now the one and only Thor, and she is worthy!"

Jason Aaron said: "This is not She-Thor. This is not Lady Thor. This is not Thorita. This is THOR. This is the THOR of the Marvel universe. But it's unlike any Thor we've ever seen before."

Marvel says that this, their eighth title to feature a lead female character, "aims to speak directly to an audience that long was not the target for superhero comic books in America – women and girls".

The original Marvel take on Thor had the thunder god's superhero alter ego as disabled doctor Donald Blake, who transformed into the god by striking on the ground an ancient cane he found while hiding from invading aliens. The cane transformed into Mjölnir, conferring the god-like powers of strength and flight on Blake. Others have since held the post of Thor by being deemed suitable to wield Mjölnir in an Excalibur-ish sort of way, but so far have been all male (though one was an alien, Beta Ray Bill).

In the movies, Thor (2011), Thor: The Dark World (2013) plus The Avengers (2012) and its forthcoming sequel, the hero is played by actor Chris Hemsworth. Exactly who will fill the thunder god's boots in the comics – whether an established character or someone completely new – has not been revealed.

Marvel Comics posed – but did not answer – the questions: "Who is she? Where did she come from and what is her connection to Asgard and the Marvel universe?"