To get from the owner of a sex-chat service to one of France’s richest men, Xavier Niel has made a few bold gambles. His latest move, a $15 billion cash bid for control of Bellevue-based T-Mobile US, is his most audacious yet.

Niel’s Iliad last month offered $33 a share for almost 57 percent of T-Mobile, a wireless provider five times larger than the French outfit.

While the approach was rebuffed by T-Mobile parent Deutsche Telekom, it was followed by news that Sprint, owned by Japanese billionaire Masayoshi Son’s Softbank, was backing off its own long-developing effort to acquire T-Mobile for about $40 per share.

The attempt by the French maverick to shake up the largest phone market in the Western hemisphere mirrors Niel’s success back at home, where Iliad rattled the wireless market with rock-bottom priced packages that have led to a two-year tariff war with incumbent operators.

Niel still risks a confrontation with Charlie Ergen, the billionaire chairman of Dish Network, who has said he’d consider picking up T-Mobile should Son’s foray fail.

“It’s a bit of a crazy move,” Borja Mijangos, a telecommunications analyst at Interdin Bolsa in Madrid, Spain, said of Iliad’s bid.

Iliad’s bid opens the most dramatic chapter in a career that is also one of France’s most unusual. A self-made billionaire who got his start with a sex-chat service on Minitel — France’s now-defunct precursor to the World Wide Web — Niel shot to prominence pioneering so-called triple-play packages combining TV, broadband and landline services.

In 2012, he took the model to the mobile market through Free Mobile. The result was a tariff battle that prompted French rivals Orange, Vivendi and Bouygues to follow suit, forcing them to eliminate jobs to help compete.

While Niel’s $33-per-share-bid is lower than the offer that had been expected from Sprint, Iliad has a key trump: A takeover by the French company would preserve the status quo of the U.S. market by keeping the same number of operators.

Niel views the U.S. as ripe for the type of disruption that occurred in France, with AT&T and Verizon Communications accustomed to tariffs that are some of the highest in the developed world, said a person familiar with the situation.

According to the International Telecommunication Union’s most recent figures, 500 megabytes of mobile data in the U.S. costs an average of $85, compared with $34.60 in France.

Niel is confident T-Mobile could increase profit even while aggressively cutting prices and its own costs, the person said, asking not to be named because the deliberations are private.

Taking control of T-Mobile US would unite Niel with John Legere, the outspoken T-Mobile CEO who has built a reputation of challenging incumbents by undercutting AT&T and Verizon, making the two corporate cultures a good fit, the person said.

Niel’s interests run well beyond the telecommunications industry. In 2010, he led an investor group that took control of the newspaper Le Monde, and has become one of Europe’s most prolific investors in technology startups. He’s taken stakes in mobile-payments company Square and music-streaming startup Deezer, among dozens of other investments.

“I’m always investing,” Niel said in an interview last October at Iliad’s headquarters in Paris. “I’m constantly in talks with someone about some opportunity.”

Though little known outside France, Niel, with a net worth of $9.3 billion according to the Bloomberg Billionaires Index, has been hard to ignore in that nation’s generally button-down business world.

Partial to jeans and open-necked shirts, he once spent time in jail when a chain of sex shops he had invested in was investigated for links to prostitution. He was never charged, and later joked that being behind bars let him catch up on sleep.

After examining offers for smaller phone assets like Orange Switzerland, Niel has figured into the largest deals in France lately. In March, he backed Bouygues’s $20 billion bid for Vivendi’s SFR unit, which was ultimately sold to cable tycoon Patrick Drahi’s Altice SA. Niel then tried to buy Bouygues Telecom, a deal that was stymied by a $4 billion price gap.

Entering a market as the No. 4 operator and having to catch up on wireless networks would be a familiar challenge for Niel. The U.S. market may also leave more room to maneuver, with carriers receiving $48.17 a month per user in the U.S. in the fourth quarter, compared with $32.51 in France, according to researcher Informa.

“He’s done a lot to bring down the cost in France,” said Alexandre Iatrides, an analyst at Oddo & Cie. in Paris. “He could be the guy to make T-Mobile into even more of a challenger.”

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