Five years ago, Lady Gaga did not exist. Then 19, Stefani Germanotta was waitressing and singing in dingy New York clubs. But she had bigger goals. "Don't ask me how or why," she sings in "The Fame," her debut album's title track, which recalls the genesis of her career, "but I'm gonna make it happen."

Gaga broke through last year as a global phenomenon, musing on "disco sticks," channeling Madonna's glitter-glam fashion, and cribbing shock-rock performance notes from Alice Cooper. Some critics say she's derivative. But Gaga has done something unprecedented, melding her inspirations with au courant dance pop and Web savvy to build a business empire notable for both the speed of its creation and the diversity of its platforms.

Now 24, she reigns over a brand that spans music (10 million-plus albums sold), video (1 billion-plus Web views), design (Monster headphones, Polaroid cameras), and marketing (HP, MAC Cosmetics). "No other artist commands the kind of attention that Gaga does," says Gabe McDonough, an exec at the ad agency DDB. "If she does something with your brand, it's like bam!–a million eyeballs."

It's hard to look away: Gaga is ubiquitous, largely because she deftly exploits the Web. "Her persona is built for the online generation," says MAC head John Demsey, with whom she created a shade of Viva Glam lipstick that has raised $2.2 million for AIDS awareness. (It was Viva Glam's most successful launch ever.) Her cultish army of fans mimic her dance moves on YouTube, uploading 15,000-plus videos. They devour her musings on Twitter, where @ladygaga has 3.8 million followers, and Facebook, where 6.4 million people have declared themselves fans. To keep them engaged, she gives thanks in real time, tweeting in support of a Tennessee student sent home for wearing an I ♥ Lady Gay Gay T-shirt and posting a photo of her tattoo that reads Little Monsters, her nickname for her fans. Her outlandish fashion sense seems tailor-made for online slide shows; she was the most-Googled image of 2009.

While other pop tarts sell tabloids and Auto-Tune their voices, the Lady cultivates her brand with near-military rigor. In 2008, she handpicked several friends to form a creative team that she calls Haus of Gaga. Together, they produce look-at-me fashions–a nude, bubble-covered bodysuit, a flame-shooting metal bustier–that define her concerts and her controversial videos, which drive a full 25% of the music site Vevo's traffic. "Bad Romance" alone has racked up some 200 million plays on YouTube; it's the site's No. 1 clip of all time.

Gaga's videos obviously promote herself, but they also tout her partners' products, such as Monster's Heartbeats headphones and HP's Envy 15 Beats Limited Edition laptop, which cameo in "Bad Romance." She features unaffiliated brands, such as Wonder Bread, using them for what she calls "a commentary on the kind of country that we are." The references "actually help her artistic statement," McDonough says. "Not having them would be like making a movie about hockey and not having ads on the boards."

Beyond serving its queen and mammon, the Gaga empire stresses social enterprise. "When we approach most artists, it's 'Here's what we want to do,' and we're done," says Ron Faris of Virgin Mobile, a sponsor of Gaga's U.S. tour. But she set conditions: The linkup had to involve her fans and her causes. So Virgin created a shrine to the Little Monsters (ladyvirgin.com) and gave show tickets to those who did community service, helping generate 30,000 hours nationwide.

She has also wowed in the boardroom. When Polaroid CMO Jon Pollock met her to discuss teaming up, he says he expected "a conversation about pink boas." Instead, she offered insights about digital strategy and how to position Polaroid to reach her generation. Impressed, Pollock gave Gaga creative control of several products. "Her design, her experience, her way of thinking all work at a different level."

The enthusiasm was mutual. Gaga proudly posted a photo of her "creative director" business card–her first–and said, "I am so excited … to, as my father puts it, finally have a real job."–Dan Macsai

For some people, fame kills it and becomes more important than the music or the performance. But for me fame is like rocket fuel. The more my fans like what I'm doing, the more I want to give back to them. And my passion is so strong I can't sleep–I haven't slept for three days.

I'm already crazy. I'm a fearless person. I think it creeps up on you. I don't think it can be stopped. If my destiny is to lose my mind because of fame, then that's my destiny. But my passion still means more than anything.

I notice on stage, I look out into the audience and there are coke cans bobbing up and down everywhere. I love the fact my fans have picked up on something I really only did as bit of fun and a comment on consumerism. My one tip is to make sure they are washed out properly!

m already crazy. I'm a fearless person. I think it creeps up on you. I don't think it can be stopped. If my destiny is to lose my mind because of fame, then that's my destiny. But my passion still means m