CEO Sam Altman famously has no equity in OpenAI, but startup bets like Reddit, Stripe and Helion have made him a billionaire anyway, a Forbes investigation found.

In the summer of 2017, Superhuman CEO Rahul Vohra started frantically messaging his investors one by one. His startup had tested out a pending update to Google’s web browser Chrome, and, due to one seemingly innocuous code change, Superhuman’s smart email service had broken overnight. The damage seemed inadvertent — no one at Google seemed to realize anyone was building on top of that otherwise dusty code — but for Superhuman, the crisis was “existential.”

The venture capital firms Vohra contacted all shrugged helplessly, claiming no direct line into the right person at the Googleplex. By Friday night, Vohra turned to messaging his angel investors, including Sam Altman, OpenAI’s CEO. “I just so happen to be at a party standing next to Sundar [Pichai],” Altman wrote back in minutes, name-dropping Google’s CEO. “Standby.”

The next morning, a vice president at Google reached out with an apology and an invite to the tech giant’s San Francisco office. In the years since, Superhuman has enjoyed a close partnership with Google, Vohra says, including being asked to test out more recent changes to Chrome. All because of Altman, who had decided to invest, through a personal fund he managed, after a single 30-minute meeting a year before. “Sam stuck his neck out for a founder of a startup that was, for him, a small investment,” Vohra tells Forbes. “But for us, it was a crucial moment in our trajectory.”

In the right place at the right time. Seemingly endlessly well-connected. Fast-moving and decisive. Founders backed by Altman echo such observations of the OpenAI CEO, who has become increasingly a household name since the rise of ChatGPT in late 2022 and the explosion of interest around generative AI. Altman has little time for startups these days, he told Forbes recently. But he remains at the top of cap table wish lists for the cachet and such ‘in case of emergency, break glass’ situations.

“Sam is rare in that he’s a capable investor, but he’s also making bold bets,” says Reid Hoffman, the LinkedIn cofounder and former longtime OpenAI board director. “A lot of investors are fearful of failing. They invest in things that will make money, but aren’t going to be potential big public failures. Sam is very comfortable with taking the big bet.”

And it’s those investments, not $80-billion-plus valued OpenAI — in which he has consistently asserted he holds no equity — that land Altman on this year’s Forbes list of the world’s richest people for the first time.

A founder turned partner and president at Y Combinator who has invested out of a number of funds over his career, Altman maintains a maze of holdings that are not well understood. Forbes sifted through more than a dozen regulatory filings and spoke to more than a dozen people familiar with Altman’s investments to reach the most thorough estimate of his net worth so far: $1 billion, enough to make Altman a new billionaire.

Altman’s personal collection of technological artifacts, for example — described to Forbes by Hoffman as including jet engines and Bronze Age swords — could not be appraised.

The lion’s share of Altman’s wealth comes from startup investments that range from early-career stakes in YC companies, like recently-public Reddit and fintech unicorn Stripe, to more recent big bets, like nuclear energy company Helion and longevity startup Retro Biosciences. Forbes estimates that his share of the funds through which he made some of such investments, including Hydrazine Capital and Apollo Projects, is worth $145 million. Large checks written to Helion and Retro account for another $555 million. The rest of Altman’s wealth comes from estimated stakes in Y Combinator funds, about $90 million of real estate in California and Hawaii, and several smaller personal bets.

That’s only what Forbes was able to track. It’s possible, sources told Forbes, that Altman retains other sources of wealth yet undiscovered. (Altman’s personal collection of technological artifacts, for example — described to Forbes by Hoffman as including jet engines and Bronze Age swords — could not be appraised.)

Some are still skeptical that Altman doesn’t have any financial upside in OpenAI; Altman’s only interest in the company was indirect, through YC’s small investment, said OpenAI spokesperson Hannah Wong. He does not retain financial upside in OpenAI today, she added. It’s an unusual situation, given OpenAI’s capped-profit and non-profit structure, and it would otherwise be “difficult to imagine” that a cofounder and CEO of a large for-profit company does not have a financial stake in it, said Song Ma, associate professor of finance at the Yale School of Management: “That’s kind of how capitalism works.”

Altman declined to comment for this story. But in a 2020 Forbes interview, Altman attributed much of his investing success to an eye for people. “Something I have cultivated over my entire career, which I think is the way I have had the most success, is finding super-high, but as of yet unidentified, talent.”

Altman’s personal mythology usually begins in suburban St. Louis, where he learned to program and disassemble a Macintosh computer at the age of 8. After enrolling at Stanford to study computer science in 2003, Altman dropped out to start location-sharing mobile app Loopt two years later, participating in startup accelerator Y Combinator’s first-ever cohort in Cambridge, Mass. alongside Reddit’s Alexis Ohanian and Twitch’s Justin Kan. At YC, Altman quickly made an impression on cofounder and president Paul Graham, who in 2009 included the young Altman on a list of the previous 30 years’ five most interesting startup founders, alongside Apple’s Steve Jobs as well as Google’s Larry Page and Sergey Brin.

Even while running Loopt, Altman started investing in his entrepreneurial peers. In 2010, he invested “small amounts” in four companies, he wrote on Reddit. The following year, Altman became a partner at YC, a part-time role helping to select, invest in and mentor startups in its batches, while sharing a portion of future profits. (Graham and YC’s founders took most of such upside, or carry, reserved for the firm, two sources told Forbes; Graham declined to comment through a YC spokesperson.)

“It’s common to make more money from your single best angel investment than all the rest put together.”Sam Altman

In 2012, Altman sold Loopt. The startup had elevated his profile in the Bay Area — including at one point presenting at Apple’s popular WWDC conference wearing layered neon pink and green polo shirts — but the price tag was relatively modest: $43 million. Altman poured some of the proceeds into a $20 million venture fund he launched that year, Hydrazine Capital, under the mentorship of PayPal cofounder and billionaire Peter Thiel. With Thiel as its anchor investor, per two sources, the fund invested 75% of its capital into YC companies, according to a 2016 profile in the New Yorker. Thiel declined to comment.

With these investments, Altman began to taste greater financial success. Five of his first 40 investments were worth 100x their invested capital, Altman wrote on his blog in 2014. The best investment, as Altman disclosed at a StrictlyVC event last year: payments company Stripe, an early YC alumni in which he invested via handwritten check before the business was even officially registered.

When Graham decided to step back from running YC in 2014, he hand-picked Altman to be his successor. Altman’s five-year tenure as YC president was one defined by expansion, setting up the accelerator’s Continuity fund to keep investing in YC alumni companies as they grew, and adding a number of programs, including online courses for would-be founders and investors, and a conference for finding “future Elon Musks,” as he told Forbes at the time. (In 2023, current YC president and CEO Garry Tan abruptly shut down Continuity, as detailed in a recent Forbes profile. Altman told Forbes in February that the move had been a personal surprise, but that it was important for YC to remain “constantly experimenting.”)

For Altman, the extra project was OpenAI, the non-profit he cofounded in 2015 with Musk and others to build a highly-autonomous system smarter than humans, or “artificial general intelligence.”

As CEO, Altman flattened the pay structure for the firm’s senior partners, including himself, so that all received similar portions of YC fund profits raised during this period, including Continuity’s $700 million first fund and $1 billion second fund, according to a source familiar with their structure. (YC declined to comment.) Altman also continued to personally invest — still mostly making bets on YC affiliated startups, such as Helion, which he said he encouraged to go through the program in 2014, and Superhuman, whose CEO Vohra had participated with a previous company. In 2015, Altman was featured on Forbes’ first-ever 30 Under 30 list for venture capital.

But while YC partners were known to work on side projects — Altman himself had first joined while running Loopt — such projects could potentially conflict with YC. That had proven the case with Tan and Ohanian, who invested out of venture capital fund Initialized Capital while still YC partners, then departed under Altman’s presidency to work on the firm full time (with a stop for Ohanian back at Reddit in-between).

For Altman, the extra project was OpenAI, the non-profit he cofounded in 2015 with Musk and others to build a highly-autonomous system smarter than humans, or “artificial general intelligence.” Altman’s transition to OpenAI was messy. In March 2019, YC announced his departure; three days later, OpenAI announced a new capped-profit entity that would allow it to raise larger sums of money, with Altman as its CEO. The Washington Post later reported that Graham had personally flown back from England, where he lives with his family, to fire Altman during that period. In February 2024, Altman told Forbes: “I definitely wanted to run OpenAI full time, so that is a very different thing.” Graham and Altman both declined to comment through OpenAI and YC spokespeople.

Altman didn’t stop investing, even after taking the OpenAI gig. During Covid-19 lockdowns in 2020, he announced Apollo Projects, a new fund to be led by brother Max, with Sam and his other brother Jack advising. The fund’s goal was to invest in “moonshots” that he told Forbes had been historically underserved by Y Combinator’s focus on software startups versus “hard tech” during his tenure.

“99% of my time is OpenAI, so this is a waste,” Altman joked in 2020 about the effort. “But it’s wonderful because I get an excuse to hang out with my brothers, and I deeply care about this segment.”

Just after he sold Loopt, Altman wrote a blog post touting the “power law” theory of startup investing: “It’s common to make more money from your single best angel investment than all the rest put together.”

Altman’s investment portfolio appears to have been modeled off an appreciation of that approach: a bifurcated strategy of smaller, speculative bets mixed with several highly-concentrated, larger positions where he keeps much of his wealth. One can lead to the other, as was the case with Reddit, in which Altman and Hydrazine led a $50 million funding round in 2014 and Altman took a board director seat. He continued to invest in subsequent rounds for the next seven years; he and his funds now control a stake worth $580 million as of market close on April 5, though only an estimated 14% is part of Altman’s personal wealth — the rest belong to the funds’ other investors, filings indicate. (Altman’s second Hydrazine fund holds the bulk of it: $470 million in shares, close to half of the fund’s entire gross asset value, according to filings.)

Another big position is believed to be Stripe, Altman’s self-described highest-performing investment, which reached a $95 billion valuation in 2021 and more recently announced a tender offer for employees at a $65 billion valuation in February. In 2020 and 2021, as Stripe’s value soared, Altman shelled out $43 million for a Hawaii mansion, and $27 million for an upgraded San Francisco house. Guests at Altman’s 950-acre Napa ranch purchased in December 2020 have jokingly called it “the house that Stripe built,” a source with knowledge told Forbes. Stripe declined to comment. OpenAI spokesperson Wong disputed that, adding that Altman’s stake in Stripe is not liquid.

“Sam’s investment philosophy is rooted in his deep conviction in the founders that he supports and his belief in their potential to propel human progress.”Josh Kushner, Thrive Capital founder

But Altman’s boldest bets are the two large investments he made into experimental startups Helion, which announced a nuclear power purchase deal with Microsoft in 2023, and Retro Biosciences, which aims to add 10 years to the average human lifespan. Altman invested $375 million personally (not on behalf of others) into Helion’s 2021 funding round after the company struggled to raise funding, Altman told Forbes in 2020 and a source with knowledge confirmed. Altman’s $180 million bet on Retro, announced in mid-2022 as from an anonymous investor but later revealed by the MIT Technology Review, consisted of at least 90% Altman’s personal capital, according to a source close to Retro.

“I basically just took all my liquid net worth and put it into these two companies,” Altman told the MIT Tech Review in 2023. “We’re very fortunate to have Sam as an investor and a strategic resource,” Helion CEO David Kirtley said in a statement. “He takes a big picture perspective on some of the world’s toughest problems and backs innovative solutions that can have real impact.” Retro’s CEO, Joe Betts-LaCroix, declined to comment.

Multiple investor peers of Altman, who asked to speak anonymously for fear of jeopardizing business relationships, told Forbes they were baffled by the size of those checks, which to them suggested that either Altman had other, secret sources of wealth (perhaps an early bet on bitcoin, one mused) or that he was willing to risk an unusually high percentage of his net worth on just a couple startup bets. Such an approach would be rare but not unprecedented, says Steve Kaplan, a professor at the University of Chicago’s Booth School of Business. Musk, a former collaborator turned critic who recently sued OpenAI, famously poured his PayPal earnings into Tesla and SpaceX at great personal risk. And Apple’s Steve Jobs did the same to set up Pixar before his return to the tech giant.

“I once got the advice from a mutual friend to spend Sam’s time like money, so I’m very frugal with it. But when I spend it, and ask him for help, he’s immediately there.”Jeeshan Chowdhury, CEO of psychedelic therapeutics startup Journey Colab

One fan of Altman’s approach: Thrive Capital founder and billionaire Josh Kushner, an OpenAI investor who lobbied behind the scenes for Altman’s reinstatement following a coup attempt by OpenAI’s former board in November, and whom Altman has said invests in a similar style. “Sam’s investment philosophy is rooted in his deep conviction in the founders that he supports and his belief in their potential to propel human progress,” Kushner wrote Forbes by email. “His capacity to dream might seem implausible to some, but his vision for the world is important for a better future.”

After a decade-plus of investing, Altman’s funds aren’t small. Hydrazine Capital’s four funds boast $1.7 billion in gross assets, with another $500 million held by Apollo Projects’ fund, per March regulatory filings. Most of that is held on behalf of others, not Altman, four lawyers and experts who deal with registered investment advisors like Altman’s firms confirmed with Forbes. (Altman is no longer actively investing through the funds, according to OpenAI’s Wong. Altman’s recent investments — including Helion and Meter — were personal checks outside of his funds.)

But for founders Altman has backed recently, the experience is still much more akin to taking money from a small-check personal investor, several said — even if that doesn’t entail a rescue mission chat with Google’s CEO, as was the case for Vohra with Superhuman. Will Jarvis, CEO of automated property assessment startup ValueBase, in which Hydrazine led a $1.6 million funding round in 2023, said Altman decided to invest within 24 hours, after asking just four questions.

“I once got the advice from a mutual friend to spend Sam’s time like money, so I’m very frugal with it. But when I spend it, and ask him for help, he’s immediately there,” says Jeeshan Chowdhury, CEO of psychedelic therapeutics startup Journey Colab, whom Altman also backed through Apollo Projects. “I’ll see on the news that he’s meeting with a world leader or doing some very important thing, and I still get a reply.”

According to Anil Varanasi, who raised a $35 million round co-led by Altman in February, Altman’s investments broadly fit within a framework of the world he imagines developing alongside OpenAI’s super-intelligence. Beyond additional AI investments, Altman believes such a world will need abundant energy and new kinds of biomedicine, including in longevity, three founders backed by Altman say.

And while some see Altman’s startup investing as a distraction or potential conflict, such investments ultimately benefit Altman’s goals at OpenAI, argues Hoffman, who has known him for more than a decade. “He’s always happy to make money, but he’s doing it to seed the ecosystem to maximize the chances of OpenAI being successful, and it’s beneficial to the AGI mission,” Hoffman added.

Altman has described this approach in a 2021 essay called “Moore’s Law for Everything,” Jarvis, the ValueBase CEO, noted. “A great future isn’t complicated: we need technology to create more wealth, and policy to fairly distribute it,” Altman wrote in that essay. “Everything necessary will be cheap, and everyone will have enough money to be able to afford it.”

This story has been updated to include additional information from OpenAI.

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OpenAI Made Sam Altman Famous. His Investments Made Him A Billionaire.