'BOHEMIAN.' The word comes up when discussing the French designer Isabel Marant. She grudgingly accepts the inescapable. 'I hate to be put in a box,' she says. 'It's difficult to accept, but it's not a bad tag. I'm bohemian in spirit.'

Although it accurately describes Marant's iconoclastic, freewheeling approach to life, as well as many of her enormously popular creations, from lace minidresses to fringe boots, it minimizes the scope of Marant's designs and her puritanical work ethic. Her attitude toward the business of fashion, however, is distinctly laissez-faire.

'I never dreamed of being a big designer,' Marant, 46, says. 'I don't care about being known all over the world.'

Despite her ambivalence, she has become a runaway fashion success story, born on the back of her trademark look, which can be described as equal parts rock 'n' roll, California surfer girl and insouciant Parisienne. Her line caters to those who aspire to passions beyond clothes but have the means to buy-and buy a lot. Since the inception of her namesake label in 1994, sales have increased at a steady 30 percent each year-even during the economic downturn-allowing her to prosper as an independent label in an era of behemoths like LVMH, Prada Group and Kering. There are 13 of her sparely designed Isabel Marant boutiques in countries from South Korea to Lebanon, and both of her lines (there is also a diffusion label, Isabel Marant Étoile) are carried in 800 retailers worldwide. This November, she will join the ranks of Stella McCartney, Versace, Lanvin and Karl Lagerfeld as the next designer to collaborate with global mass retailer H&M, where she will also debut a men's collection.

It's a long way from her first fashion show in a Paris squat nearly two decades ago, when her designs were sought out by her friends: fashion editors, stylists and the models who walked her runway. Their nonchalant combinations of Marant's casually sexy jeans and T-shirts with a cropped jacketperfectly slung over their shoulders introduced a new fashion vernacular and quickly garnered attention from street-style photographers and beyond. Initially, however, Marant remained largely an insiders-only secret. 'I remember when Sofia Coppola and Gwyneth Paltrow came to my shop in Paris and brought stuff back to the States,' she says. 'It didn't exist anywhere.'

Today, 90 percent of the company's sales are outside of France, and 25 percent in the United States. 'We have some customers who call every week asking about new deliveries,' says Jennifer Sunwoo, an executive vice president at Barneys. 'They pore through the lookbook each season to reserve items long before the styles hit the floor.'

Marant declines to acknowledge these measures as the standard of success. 'I once said that I'm anti-consumerist, and that goes against the work I do,' she says. 'It caused a scandal: 'Who is she to think that? She is going against her clientele.' But I do fashion because I'm happy when somebody gets joy from a new garment. There is a magic side to this.'

ON A GRAY PARIS DAY in late June, Marant is sitting at a gleaming white table in the spacious two-story atrium of her headquarters just off the Place des Victoires. Errant sunbeams pierce the clouds and illuminate the vast concrete-floored space. In front of her is a vase of white peonies and jasmine. She wears a loose sweatshirt with 'Mister Freedom' written on it, the frayed collar stretched out and exposing the straps of her black tank. Her look is rounded out with gray corduroys, a studded black leather belt and ballet flats.

'I always wear my own clothes,' she says. 'My sweatshirt I got in L.A., but the rest is Isabel Marant, like 99 percent of my wardrobe.' She laughs and adds, 'I get a good discount. She's very nice to me.' In fact, Marant always begins her design process with herself and her own desires. 'I don't dress up every day. I wear a sweatshirt and a trouser, like most people. From this starting point, [I ask myself], How do I make this silhouettefashionable and stylish?'

'It's about the women surrounding me,' she continues. 'I look at how women in the street wear things. I've never been inspired by a muse-that's a fantasy.'

It's no surprise that Marant doesn't bother doing eveningwear: In punk parlance, she is more Patti Smith than Deborah Harry. Her greatest hit, a clever high-top suede sneaker called the Bobby that camouflages an interior wedge heel (which sells for about $650 and is often marked up to around $850 on eBay), is perhaps the best distillation of her dressed-up version of dressed-down cool. With the Bobby (soon followed by the Bekket, a pumped-up variation with Velcro straps), Marant created a new staple of the women's contemporary wardrobe-and today, seemingly every brand that produces footwear makes a version. When asked about knockoffs, from which she often suffers, Marant exhales and says in a measured tone: 'You are super pissed-off, but if you are not copied, it means you are not 'the one.' What I don't like is that it spreads your style everywhere. Something you are doing gets old in a minute. It takes such time to achieve something well and find the right way of doing things. But what can you do?'

Following her instincts has generally served Marant well. 'Usually my favorite is what is going to sell,' she says. 'It's rare that something I really love doesn't sell. It honestly almost never happens. With the sneakers, I knew it was something. I said, 'That's going to be a hit.' I can feel it when I do something right, and I can feel it when I do something only so-so.' She continues, 'During my entire career I've done maybe five pieces like this. It's rare-when it happens your heart is beating.' (The other items she counts in this stratosphere are perennials like the Dicker suede ankle boots, as well as her washed linen T-shirts, embroidered jeans and a men's overcoat that has appeared in many iterations.)

She begins rolling a cigarette. Her process is arduous. 'This takes time,' she says. 'Instead of smoking a pack a day, I smoke four cigarettes. I spend less and smoke less.' She doesn't buy loose tobacco, instead buying a pack of Bastos cigarettes. She shreds one and empties the tobacco into a candy tin. She then pulls out the rolling papers. 'I quit smoking for a year, and I gained 10 kilos [22 pounds],' she says. 'It's not me. I was not feeling myself anymore. It was breaking my brain.'

In person, Marant is a strikingly natural beauty. She wears no makeup and her hair, a multitude of varying shades of gray and amber, is pulled back in a messy bun. 'I think sometimes I should dye it,' she says. 'And then I say, 'No, Isabel. That's how it is. Don't worry. That's life.' ' When she smiles (which is often), her entire face creases and the ends of her large, toothy mouth almost touch her eyes. She is gracefully slim, and her uniform of menswear staples only serves to heighten her femininity.

Her low-key look seems to be part of her emphaticrefusal to partake in the pantomime of the fashion swirl. 'I'm not this goddess of fashion-I'm low profile. I look like a delivery guy,' she says. 'I drive my scooter and always have my helmet on. When people meet me, they think this cannot be her, because I look like a bum.'

Her eclectic design ethos had its beginnings in Marant's own family. Her father, a photographer, had already been divorced once before marrying her mother, a German model. (His first marriage didn't last long, but produced a half-brother). After Marant's mother, her father's next wife was a Caribbean