"THE women in The Mai, they're basically waiting for their prince to come."

"Don't you think that happens all the time?"

That happens all the time, Marina Carr. What is rare is for a young woman writer fearlessly to put the emotional reality at the heart of so many women's existence on stage. Effortlessly to slough off the need to politicise her woman's voice. And with this voice, to occupy a stage of the National Theatre fought over by battalions of male playwrights for nearly 100 years.

She is an unlikely heroine, this slim, attractive 31 year old, constantly sucking on a cigarette: "I started writing before I knew how or why," she says. "I just assumed - I had a right to be there. If you thought about the political agenda, you'd drive yourself mad." She is absolutely possessed by her art, and interview arrangements broke down repeatedly because Carr is wrapped up in the rehearsal process for her new play at the Peacock, Portia Coughlan, directed by Garry Hynes.

"The name came to me first, the rest came after. I started writing just using the name - I didn't have a theme. I just wanted to write about a woman from the Midlands called Portia Coughlan." The name comes, she explains, from The Merchant Of Venice. "Not the Coughlan, surely?"

She won't give me a script. It's still changing. It's about Portia's haunting by the death of her twin brother 15 years before: "In all of us there's a twin," she explains. "That shadow part of you is often the best part of you. That identity has been fudged or subsumed in Portia, and in a sense she's like a walking ghost herself."

"I'm fascinated by the twin motif," she says. "From Isis and Osiris to Hero and Leander or Siegfried and whoever it was . . ." The gender difference is important too - there is a sexual charge in the relationship between Portia and her twin - and it is interesting how twins of both genders make one whole being in mythology, as if good old Jung was right about the male and female parts in all of us.

Portia's twin, an aspect of her that is dead, or dying, that is calling to her I think, has left her a husk identity, which does have a certain feminist logic to it, all the same: "She doesn't know who she is and who she should be," says Carr. "The play is about her fight to stay in the world on her own terms.

Mind you, she is, as her mother would say as most women's mothers would say not doing badly. Just 30, she has been married for 13 years, deep in the Mid lands, to a factory owner called Raphael, who is dark, brooding, and would do anything for her. They have three sons. Still bored? Well, she has a lover too. But all of this is not enough for Portia Coughlan.

And it is not enough for Marina Carr you can't catch her art in the net of a plot. The Mai, which ran during the Dublin Theatre Festival in 1994, was the first of her plays in which a truly original voice emerged; it toured to Glasgow's Mayfest and earned Carr a comparison to Eugene O'Neill in the Observer (interestingly, he is one of her favourite playwrights, along with Tennessee Williams). In it Carr first conjured up the magical Midlands landscape which she also uses in Portia Coughlan.

The Mai, commissioned by Garry Hynes during her artistic directorship of the Abbey, is the harrowing story of a beautiful, capable 40 year old woman, whose sadly inferior husband has left her. But she will not give up. She builds him a mansion on the shores of Owl Lake and sits at the window beaming to him the words: "Come home".

Through this life, Carr summons up all the resourcefulness and energy of women's romanticism; and undercuts it savagedly. Julie, the Mai's plain aunt, says casually: "It's not fair they should teach us desperation so young or if they do they should never mention hope.

Her earlier work was strongly influenced by Beckett, as Carr is quick to acknowledge - she began a Master's on the writer in UCD. Low In The Dark, which was performed at the Project by Crooked Sixpence in 1989, is an extraordinary piece which hilariously and ruthlessly rips the stuffing from the motherhood myth, with pregnant tummies ballooning up on men and women all over the stage; and centres, too, on the sad lack of understanding between men and women: "I want a house with a bath and a man in it and a baby, all together, all forever, all for me," says Binder, and Bone replies: "I want a permanent relationship for a month or two." Ullaloo, another absurdist piece, opened at the Peacock in 1991 - and closed not long afterwards, having had vigorously mixed reviews.

Living on "tuppence" and during an absence of the boyfriend she married last year, she went to Annaghmakerrig and began the graft of writing The Mai, a well made play: "I wanted to learn how to write - I thought the way to start was with the basics. Learn the rules before you break them."

After she had written The Mai, the Holles Street Hospital Centenary Committee, which included Garry Hynes, dreamt up a brilliant scheme to commission Portia Coughlan by recruiting 100 people - mostly career women to donate £50 each to the process. Carr was given a little antiseptic room in the hospital overlooking Merrion Square, in which to write, and did some workshops with the staff. The matron, Maeve O'Dwyer, has told her she can have the room as long as she likes, which will be, says Carr, "when I'm wheeled out".

She has the commissions stacked up: Portia Coughlan is due to open at the Royal Court in May, and that theatre has commissioned another play, as has the Abbey; the Project and Druid have also staked their claims. All she wants to do is keep writing: "I plan to live to be 90, so that's 25 plays?"

That's not counting the sketches she started writing as a small child growing up in a family of six in Co Offaly, in a place near Tullamore called Pallas Lake: "Called after Pallas Athena. Well, I think it's Pallas Athena. I'd like to think that." It's a good indication of how her art is being created at present, by turning her own landscape to magic. Portia Coughlan is set on the Belmont River: "There's a place called the Belmont, I don't know if there's a valley. I imagine it." Offaly is full of exotic names, she says: "Rhodes", and "Rue de Rat". She is fascinated by the "very particular English" of the county, and has written Portia Coughlan phonetically.

The portrayal of a kind of rural life is very important to her: "These people, they're peasants who got rich. They may have wine for dinner every evening, but the way they'd handle the wine glass".

There's a great distance between them and the world they inhabit. There isn't much refinement, and yet there's a curious refinement which they have no respect for, and the world has no respect for."

She has not cut herself from her rural roots: "I thought I was sophisticated, but I'm not. I've been told." With a great laugh she says: "I'm a little married woman, really. A little bog woman.