It's a sweltering mid-June morning, barely two months before the much-anticipated opening of the SLS Las Vegas, and the resort site is in a state of utter pandemonium. Hundreds of hard-hatted workers race in every direction, armed with drills and saws and hammers. Clouds of chalky white dust waft through the air, enveloping the giant acid-yellow chair that is the only piece of furniture in the lobby. The hotel's main tower is only half-painted. The pool is drained and only partially finished. And every few minutes, an errant fire alarm emits an ear-splitting shriek.

Standing on a debris-filled balcony 23 stories above the madness, Sam Nazarian surveys the scene with Zenlike calm. "We still have a few things left to do," he says with characteristic understatement. "But failure is not an option." Nazarian, the 38-year-old (he turns 39 in late July) founder, chairman, and CEO of the entertainment company SBE, is one of the most prolific nightlife entrepreneurs in the world. The SLS, built on the bones of the venerable Sahara hotel, is the biggest gamble of his risk-filled career—a nearly $1 billion bet on a city that is just emerging from the most bruising recession in its history. After Nazarian's amazingly rapid ascent, many people are eager to see him fall. But if he feels the pressure, he doesn't show it.

Instead, as we tour his unfinished new palace, Nazarian is as giddy as a college kid showing off his first apartment. A genial six-foot-four figure clad in a shiny white silk jacket and a black T-shirt and jeans, he looks more like the MC of a lounge act than the CEO of a global hospitality empire. At the entrance to his new casino, where the freshly paved parking lot bubbles under the midday sun, he directs my attention to the giant, new five-sided marquee. "We hired the finest telecom firm in South Korea to design this for us—they do these 3-D graphics that are so real you'll think you're tripping." Inside the cavernous space that will house the hotel's nightclub, Life, he points out the flimsy catwalks where acrobatic models will dive and pirouette to entertain the throng below. We pause in the lobby to admire the plush Turkish rugs and exotic acid colors selected by the designer Philippe Starck. We wend our way through the thicket of hip eateries that have sprouted up—the Nascar Cafe and its ilk are distant memories—and the hundreds of brand-new, gleaming slot machines, grouped like sentries in the center of the casino floor. We even make a pit stop in a musty storeroom, where a set of stainless-steel doors will open Star Trek–style to reveal Nazarian's secret office.

But the high point of the tour, as far as Nazarian is concerned, is the 23rd-floor penthouse, which once hosted some of the world's biggest stars. "You realize that you are in the exact spot where Elvis used to sit for six months?" he asks. "You're looking at the same view that Marilyn Monroe and the Beatles once did!" Sprawled out below us is Vegas in all its cheesy, fabulous glory: the famous Stratosphere, a check-cashing place, a new Walgreens, the skeleton of the half-built Fontainebleu—abandoned during the recent recession. In the distance you can see the pristine ring of red hills where Nazarian lives. Though he still keeps a penthouse apartment in Los Angeles, Nazarian spends most of his time here at an $8.5 million, 14,000-square-foot, triple-gated mansion with a 10-car garage, a home theater, and other amenities.

But Nazarian turns his gaze straight down, contentedly taking in the forklifts, the scaffolding, and the army of scurrying hard hats working overtime to realize his grand ambitions. "A few years ago, when it looked like I might lose this place," he says, "I used to come up here to the penthouse every day and hide out. I'd sit and think, How the hell do I get out of this mess? But these days I come up here and I can't believe we've made it happen." Owning the place where Elvis once sat, Sam Nazarian finds it hard not to feel like a king.

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Every aspiring tycoon can recall his rocket-ship moment: that precise point in time when his career either soars into a rarefied stratosphere of success or fatally plummets back to earth. For Sam Nazarian, that moment will arrive at exactly midnight on August 23, when the SLS Vegas officially opens its doors.

Nazarian was just 31 when he bought the Sahara in 2007, at the height of the Vegas real-estate boom. To some, the move smacked of hubris. But to Nazarian, a casino was the logical extension of a hospitality empire that had exploded in less than a decade to include more than 40 nightclubs, restaurants, and development projects. Today SBE owns a sprawling archipelago of brands, from nightclubs like Hyde, Greystone Manor, and the Sayers Club to restaurants like the Bazaar by José Andrés, Katsuya, Cleo, Umami Burger, and 800 Degrees to venerable, money-minting watering holes like the iconic gay bar the Abbey.

But while Nazarian earned his stripes in nightclubs, what turns him on most is hotels. He launched his first new hostelry, the SLS Beverly Hills, in 2008, taking over the bankrupt Le Meridien. Then, as now, there was lots of skepticism. But after a rocky start, it has become one of the most successful hotels in the city. He opened his second SLS in South Beach in 2012, across the street from Ian Schrager's storied Delano, which had been designed by Starck nearly two decades earlier. (At the opening, Rumer Willis performed on a stage floating over the pool while videos of giant monkeys were projected on the walls.) He plans to open new SLS outposts in Boston, Seattle, Philadelphia, Austin, and Shanghai by the end of 2017. He owns a hipster hotel called the Redbury, with branches in Hollywood and South Beach. He's launching a chain of upscale gay hotels with the founder of the Abbey, reportedly the top-grossing gay bar in America. And at the end of this year he is opening an SLS at the massive Atlantis-like five-star resort in the Bahamas, called the Baha Mar.

"What he's done is truly spectacular," marvels the director Brett Ratner, a pal of Nazarian's who met him at one of his nightclubs. "When I was in Miami a few months ago, he took me on a tour of the SLS there and I was blown away. When we met, Sam was just a club guy, a small-businessman. But suddenly I turn around and the guy owns the whole entire world."

• • •

It is quite possible that Sam Nazarian owes his success to the fact that he was a loser in high school. Nazarian may quarrel with the language—"I would say loser is a very strong word"—but not the notion that his outsider status helped fuel his uncommon drive. As the youngest child of a wealthy family described as the "Persian Rothschilds," Nazarian certainly enjoyed a high level of privilege. But rich kids are a dime a dozen at Beverly Hills High, where an unspoken divide between the Persians and "the whites" persists to this day.

"When I was growing up, there was a definite sense that Persians were just invading L.A.," he says. "And the truth is, we were just not cool. We didn't know how to dress. We didn't know the culture. Every time we'd go to a club, they'd make us wait for two hours and then announce it was a private party. It was kind of sadistic." While exacting revenge was never his primary motivation, Nazarian is aware that many of the clubs he owns today would have turned him away if he weren't footing the bill. "I ended up hiring some of those doormen," he says with a satisfied grin. "Now they always let me in."

The Nazarians arrived as part of the flood of Iranian Jews that settled in Los Angeles after the Islamic revolution in 1979. The family moved into a run-down Santa Monica hotel when Sam was 3; his two sisters and brother were considerably older. His father, Younes, had grown up poor in Teheran's Jewish ghetto and went on to earn a fortune manufacturing construction equipment, only to have it confiscated by the Ayatollah Khomeini's regime. After arriving in L.A., using money they were owed by German companies, Younes and his brother started over, buying a factory that built machine parts and investing in real estate and technology. In the eighties, the brothers put some cash in an obscure communications company that went on to merge with Qualcomm. It went public in 1991, giving Younes and his family a massive windfall overnight (their share is valued today at more than $1 billion).