Baby boomer: Juno star Ellen Page goes from geeky unknown to star of this year's most talked-about film

Ellen Page isn't yet certain of her plans for her 21st birthday in two-and-a-half weeks. For sure, she knows she'll be in Los Angeles. She might have her hair and make-up done. She might be – reluctantly – trying on a parade of freebie designer dresses, attempting to ignore how ridiculous a 5ft-tall girl-woman half-pint looks in a stupendously extravagant frock. Maybe she'll be cruising through Hollywood, her in-car iPod rocking to the sounds of Sigur Ròs and Bat For Lashes, the kind of hip, brainy Euro indie music this hip, brainy Euro-friendly indie kid favours.

But landmark birthday or not, Ellen Page probably won't be celebrating, as other 21-year-olds might, by getting smashed – just in case: while the Canadian actress will finally be able to drink legally in the US come 21 February, three days later she could be anointed the best young female talent of her half-generation as the star of the smartest independent-flavoured film since Little Miss Sunshine and Sideways.

Alongside Cate Blanchett, Julie Christie, Laura Linney and experienced French star Marion Cotillard, Page has been nominated in the Best Actress category at this year's Academy Awards. Juno, the "dramedy" about teen pregnancy in which she plays the 16-year-old title character, is also nominated in most of the main Oscar categories: Best Picture, Best Director (for Jason Reitman) and Best Screenplay (for the work of sex worker-turned-blogger-turned-screenwriter Diablo Cody).

"It's incredible," says Page of the success of Juno, which has just passed the $100m mark in takings at the US box office, barely two months since it opened on a limited release. "It's completely unexpected." She has had a little while to get used to the film's phenomenal reception – it has been wowing festival audiences for six months now – but still, perched in a London hotel suite the day after the Oscar nomination announcement, she is still breathlessly processing the information. "What it comes down to is that Diablo Cody wrote one of the best screenplays I've read," continues Page, who has been acting since the age of 10 and whose biggest roles until now were as Kitty Pryde in X-Men: The Last Stand (2006), for whom walls were no object, and Hard Candy (2005), a hard-hitting cult hit in which, aged 17, she played a girl who turns the tables on a paedophile. "[Juno] is a teenage female lead that I don't think we've ever seen before," she suggests. "And although [the role] is witty and unique and funny, it's extremely honest. I think that's what has caused this connection that people have [with the film]."

Juno MacGuff is a high-schooler living in the comfortable humdrum suburbia of the American Midwest. She is clever, articulate, perhaps a little too smart. As the opening remarks of Cody's script put it, she's "an artfully bedraggled burnout kid". Juno likes Iggy and The Stooges, the horror films of Dario Argento and dressing like Kurt Cobain's sloppily comfortable little sister. She has a close male friend, Paulie Bleeker (played by Superbad's Michael Cera), sweetly geeky in his yellow sweatbands and too-short shorts (he's an unathletic member of the athletics team at Dancing Elk High). One quiet afternoon, when all that the rest of the day promises is The Blair Witch Project on telly, Juno suggests to Paulie that they "make out". Goodbye virginity, hello procreation. In short order, Juno informs her dad and stepmum of her "situation", palls at the idea of an abortion, and offers her foetal "sea monkey" to a childless yuppie couple who have placed a "baby wanted" ad in a local freesheet.

Courtesy of Fox Searchlight

With evident feeling, Page says that "to be able to be that girl" in a teen movie of Juno's calibre was an "organic" thrill. Page credits Reitman (son of Ghostbusters director Ivan and whose first feature was the razor-sharp satire of tobacco lobbyists Thank You For Smoking) with keeping the tone natural, and the 29-year-old Cody – the author of Candy Girl: A Year In The Life Of An Unlikely Stripper – with the crackling dialogue, a torrent of one-liners, wisecracks and slangy ' put-downs. "Wardrobe became really important, especially the whole fact of creating someone that we haven't seen [in films]," adds Page. "Juno wears baggy jeans and a flannel shirt or a sweater vest, and there's no need for an explanation why she dresses that way. And the people at school don't completely ostracise her. So the film doesn't go overboard. She's just a multi-dimensional, whole, honest person."

Ellen Page grew up in Halifax, Nova Scotia. Her parents (dad a graphic designer, mum a teacher) weren't thespian types. A relatively isolated town, it wasn't like Toronto or Vancouver (where, for cost reasons, many Hollywood productions shoot), far less Los Angeles. "Acting is nothing you'd think of in Halifax," she says in her mild Canadian accent, "but I always feel like I had a very vivid imagination. I was in the drama club at school and loved theatre and so on and so forth." So when a casting director visited her school when she was 10, Page was intrigued. He auditioned her for a part in Pit Pony, a drama set in the local Cape Breton coalfields at the turn of the last century. She got the part, which then turned into a recurring role in a spin-off TV series. Jobs on a range of Canadian films followed, and Page spent more and more time on her own on filmsets. But she worked to maintain as normal a life as possible. She played football competitively, for instance – because of her soccer days, she was well aware of Vinnie Jones and his reputation when they appeared together in the X-Men movie: 'I knew of the famous ballsack grab!'

She also maintained her interests outside acting, such as history – last year she and a friend backpacked around Serbia and Romania, because she's long been fascinated by that part of the world ("Obviously Romania's gone through so much transition, and will continue to go through a lot of transition as the capitalist West looks to do what they do"). And, at her own choosing, she attended a Buddhist high school in Halifax. Not because she, or her parents, are Buddhists. No, she was drawn to the educational values offered in the school, which was run by the Shambhala branch of the faith – Page says that alongside Boulder, Colorado, Halifax is the Buddhist capital of North America. "The whole school would meditate together at the beginning of the day, and my class went camping, on aboriginal animistic retreats," she says. (It is an enthusiasm that persists to this day in her choice of reading material: the charmingly geeky and super-polite Page loves non-fiction books about modern shamanism, such as Breaking Open The Head, by Daniel Pinchbeck, as well as ancient cultures.) "If you want to be an engineer, I don't know if the school necessarily has the resources to propel [you] to that extent," she adds. "Maybe that's a bad thing to say, but it definitely leans towards more of a liberal arts area."

Switched-on, sensible young Page kept her head: aged 13, she was offered a part in an American sitcom. It would have meant moving to LA. She and her parents decided it was a bad idea. She might have made a splash in Hollywood a lot sooner. But equally she could have been a Lohan- or Britney-shaped burnout. "Yeah, and it definitely happens to some people and it doesn't to others." She sighs. "It's really unfortunate – I wish there was more compassion for those people versus just relentless judgments. It's sickening. I feel bad, you know – they were hyper-sexualised at the age of 16, not guided or taken care of or nurtured properly." Just exploited. "Completely!" she exclaims. "And now people treat it like it's a joke. Let's splatter their face on newspapers every day and show them being taken out of their house on a stretcher! It's like, why don't we ask why this is happening? It makes me very angry." This is clearly a topic she's thought a lot about. No wonder, perhaps, that she shares a publicist with Natalie Portman, another alert young actor.

This watchfulness will stand her in good stead on her next project: this summer she's shooting the lead role in Whip It, the directorial debut of Drew Barrymore. "I play a girl in Texas who's forced to be in beauty pageants but instead she runs away to Austin and joins a roller-derby team." You can see why Barrymore, who infamously battled all manner of addictions while an adolescent, would be drawn to a young actress of Page's calibre and smarts.

But before all of that there is the ongoing phenomenon that is Juno. The role of a troubled-but-sparky 16-year-old suddenly dealing with the messy world of adults was, says Page, a gift. Such well-rounded characters are difficult to come by for young actresses – "or any female actor at any age". She herself isn't offered many "cheerleader movies", because her agents know "who I am and what I like". Nonetheless, "one thing I really notice is that I will read a script and it will be good. And I'll say, wow, this is good – the character is great for the guy, not so much for the girlfriend. Often the male is the character that facilitates their own destiny, and the female is a tool for that. So when you get a script like Juno and there's an extremely intelligent, articulate, funny but also kind of abrupt young woman, it's incredibly exciting."

Courtesy of Fox Searchlight

The Academy Awards will offer this gifted young woman excitement of a very different order. "Oh, it's something I don't think about," says Page when I float the "what if you win?" question. "It's absolutely mental, as you guys would say. It's ridiculously humbling to even be nominated with women I respect and admire so much. So it's not something I would ever even be thinking would happen. I mean, this I what I love to do – I'm an actor because I love to act." What the Oscar heat really means, she says, is not the fancy frock or the red carpet excitement. It means what might come next for this shooting-star talent. "What it means," says Page, "is opportunity."

'Juno' (12A) opens on Friday

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