If you include isekai, there are plenty of male oriented portal fantasies.

Neverwhere, king rat, Thomas Covenant are all fairly popular and considered portal fantasy

I’ll probably come back to expand properly when it’s not super late and I’m super sleepy but I want to bring attention to a portal fantasy book series I wish more people knew about

The Unicorn Chronicles by Bruce Coville

It stars a female protagonist for the lists all are making of boy v. girl versions lol However, it’s a 90s Scholastic Book Fair classic

I think female protagonists are possibly more popular than male (I honestly cannot say what is true, I don’t know) when it comes to this specific genre is a mix of what everyone else has said but here’s my specific take (please take with a grain of salt, I’ll reiterate I’m posting under the influence of sleep):

(Also note I was born in 1990 Ontario Canada a cis woman, so this is my specific perspective)

In the same way that men/boys are socially allowed to have adventures and don’t quite need another world nor a portal to make a name for themselves and be a hero, men/boys aren’t typically socially allowed to have these adventures the same way women/girls do

You know those jokes about how people expect girls to play vs how they actually do? How majority of western girls can attest to the drama they put their toys through, the very adult themes girls can act out through play as young as 6-7yrs old, it’s not coded into boys

Girls are, inadvertently or not, taught to be more emotionally mature/intelligent from the get go. We’re caretakers and peacemakers and we’re always told to let things go or get over it, don’t rock the boat, be easy and flexible because a boy needs to be loud and rough and tumble (I hope that by now these stereotypes are being thrown away; I’m not a parent, myself)

Boys can get away with anything and always get what they want. They’re boys, it’s expected that they’re mean, dirty, strong, leaders

Portal fantasy means to me, as the young girl I was and the woman I am today, the penultimate escape fantasy. Even when things are dangerous and difficult, it’s never BECAUSE you’re a girl but it resonates with you for that reason

You are your own person, you are a hero, you are liked and loved and hated and despised and it’s because of who you are, not what your biology is

It’s permission to be the boy, to experience what it’s like to be the center of attention on the forefront of everyone’s mind and there’s magic or something?? Hell yeah

I don’t feel like I’m explaining myself well enough so I’ll stop here lol

Honestly, The Never Ending Story (book of course) is, imo, more like a girl portal fantasy despite being a male protagonist

It’s more about relationships, self image, emotional/mental growth, consequences, confidence, SO MUCH weight to that story lol

Shoutout to the very fun children’s book Castle in the Attic

I always assumed a large part of it was escapism and rooted in fairy tales. Historically women and girls don’t have a lot of power, so this offers a realm in which they can have more power or one in which power isn’t a systemic concern.

I also think it allows for more fantastical conflict resolutions and a degree of separation. You can’t accidentally melt a witch with water in real life and the imagery is less concerning than a bloody and violent death.

I think most kids also know, consciously or not, that a portal to another world won’t exist. At the very least it’s unlikely, so there’s no real world witches or bandersnatch to worry about.

I don’t think this is all necessarily intentional, but I think it’s something psychologically ingrained in our patriarchal society.

Just wanna pitch my favorite male-led portal story here: the Phantom Tollbooth!

Tom’s Midnight Garden is the only one I could think of, off hand.

The Subtle Knife by Philip Pullman has a boy and girl creating and moving through portals.

The Dark Tower II: The Drawing of the Three by Stephen King has a man, woman, and boy moving through portals.

I don’t think this is actually true. There is definitely some very famous portal books with the female protagonist, which probably reflects the female reading audience for a lot of these books, but I think there’s a lot of confirmation bias going on here. Portal kids’ books with main boy characters off the top of my head include

The Phantom Tollbooth (v famous) The Hero from Otherwhere (not well known now but v popular in the 80s) Tom’s Midnight Garden (v famous, lots of awards) James & the Giant Peach (v famous) 100 Cupboards (and its sequels) Miss Peregrine’s Home for Peculiar Children The Keys to the Kingdom (Garth Nix series)…

I really think it’s just confirmation bias.

Glory Road by Heinlein. Main character is a young, adult male.

Book starts out a fantasy and ends up sci-fi. I suppose you could call it science-fantasy.

There’s a portal book by Steven king with a male protagonist I can’t remember the name though

Ten thousand doors of January is a little different… yes there’s a girl, but also a boy…

One of my favourite series is a series of portal (and reverse portal) fantasies, and the author (Seanan McGuire) actually addresses this specifically in Every Heart A Doorway:

Boys are “too loud, on the whole, to be easily misplaced or overlooked; when they disappear from the home, parents send search parties to dredge them out of swamps and drag them away from frog ponds. It’s not innate. It’s learned. But it protects them from the doors, keeps them safe at home. Call it irony, if you like, but we spend so much time waiting for our boys to stray that they never have the opportunity. We notice the silence of men. We depend upon the silence of women.”

In general, I agree with the poster who said that it’s because women have more in general that they need to escape. But when I read this passage it stuck with me, because it named a trend I hadn’t noticed until then.

No one’s mentioned Brandon Muir’s Beyonders trilogy! Unique in that the main character gets transported to an alternate world by being eaten by a hippo at the zoo.

The Magic Tree House series…the children’s book Where the Wild Things Are, plus the numerous other ones mentioned in this thread…sounds like confirmation bias, OP.

But I thing you did hit on the trend of Alice imitations.

This happens with male protagonists frequently as well. You see in children’s stories like authors Lloyd Alexander, Roald Dahl, Lewis Carroll. There are also modern examples like almost every Gaiman book lol, Fairy Tale by King or Blake Crouch.

Iirc, there’s an entire genre of Manga dedicated to this.

But I see what you mean about it being more young girls in western fiction. I always figured it was to subconciously make our lead more vulnerable or innocent as some sort of foil to the environment.