In addition to becoming a household name thanks to the resounding success of ChatGPT in 2022, OpenAI CEO Sam Altman has long been one of Silicon Valley’s most influential startup investors. Long before generative AI captured global attention, Altman established a reputation as a prolific angel investor whose bets helped shape the modern technology landscape, from his early stakes in Band, Reddit And Instacart later, high-conviction investments in nuclear power and the science of longevity.
Altman’s experience as an early-stage investor was formed during his tenure at Y Combinator, where he served as president from 2014 to 2019. In that role, he helped oversee investments in hundreds of startups, several of which became large technology companies. After leaving YC, Altman continued to personally invest in alumni companies and new ventures.
Over the years, Altman has invested in more than 400 companies through a mix of personal angel checks, his own funds like Hydrazine Capital and Apollo Projects, and partnerships with larger venture capital firms.
Altman’s investment activity in 2025 focused on startups in the areas of AI-based security, biotechnology and nuclear fusion, according to Crunchbase data. These bets reflect not only a desire to diversify into cutting-edge sectors, but also to champion “moonshot” projects tackling some of today’s most complex challenges, from increased intelligence and clean energy to breakthroughs in human health.
Here are the startups Altman invested in this year:
Helion Energy
- Product: fusion power
- Investment channel: personal investment/angel investor
- Investment: $425 million, Series F in January
- Valuation: $5.4 billion
Helion Energy is a nuclear fusion company working to commercialize fusion energy as a carbon-free energy source. The company is building its first fusion power plant in Chelan County, Washington, scheduled to come online in 2028. As data centers and advanced AI systems drive increased demand for electricity, interest in scalable, emissions-free energy has grown in the technology industry. Helion is positioning itself to meet this demand with a patented, pulsed, no-ignition fusion approach designed to produce electricity directly, without the need for traditional steam turbines. Altman has been one of the company’s most prominent backers for several years, calling Helion in 2021 “by far the most promising fusion approach I’ve ever seen.” Its latest investment came in Helion’s $425 million Series F round in January.
Mirror tab
- Product: Web Security Technology
- Investment channel: Altman Capital
- Investment: funding round of $8.5 million in February
- Valuation: not disclosed
MirrorTab develops browser-based security tools that protect customer-facing web applications against threats such as malware, automated fraud, sophisticated bots, and so-called agentic AI abuse. MirrorTab uses pixel streaming technology to prevent untrusted browsers, extensions and scripts from accessing sensitive data or code, without requiring users to install additional software. “Most Vendors Focus on Enabling AI– far fewer strive to restrict it,” CEO and Founder Brian Silverstein said at a recent conference. “Effective AI security requires knowing when to exploit AI and when to block it altogether. »
Campus
- Product: Online educational services
- Investment channel: personal investment/angel investor
- Investment: $46 million Series B in March
- Valuation: $100 million
Campus is a two-year online college offering low-cost, accredited degrees taught by faculty from institutions including Stanford, Princeton, and Howard University. Students attend live online classes and supplement their lessons with AI-generated educational tools developed by Sizzle AI. The school currently offers associate degrees in business administration and information technology, with an optional concentration in applied AI focused on business use cases. Altman backed Campus in its $46 million Series B funding round, alongside investors including Figma CEO Dylan Champ, Palantir co-founder Joe Lonsdale and Shaquille O’Neal. Altman also helps fund the company’s Shaq Scholars program, which provides financial support to enrolled students.
DriverAI
- Product: automation software
- Investment channel: Altman Capital
- Investment: $15 million Series A in April
- Valuation: not disclosed
Founded by former Palantir employees, ConductorAI focuses on automating complex government approval and compliance workflows. The company’s software, which has been commissioned by the U.S. Air Force, Space Force and Office of the Secretary of Defense, uses AI to review large volumes of policy and regulatory documents. According to Business InsiderConductorAI has primarily been used to automate security classification, with additional applications in the areas of export licensing, compliance with international arms trafficking regulations, and document review.
Exowatt
- Product: renewable energy
- Investment Channel: Angel Investing
- Investment: $70 million Series A in April and $50 million in November
- Current valuation: $140 million
Exowatt builds modular power systems designed to provide energy on demand at scale. Its technology uses Fresnel lenses to concentrate sunlight into thermal energy, which is stored in ceramic bricks that function as batteries for the system’s motor and power generator. While the underlying approach isn’t new, Exowatt is betting that new capital — from Altman, venture capital firm Andreessen Horowitz and investors including Leonardo DiCaprio — will allow it to quickly manufacture and deploy systems nationally. The aim is to serve data centers facing increasing demand for 24-hour, cheap, reliable and low-carbon energy.
Coco Robotics
- Product: delivery robots
- Investment channel: personal investment/angel investor
- Investment: $80 million Series B in June
- Valuation: $300 million
Altman was a lead investor in Coco Robotics’ $80 million Series B round in June 2025. The Santa Monica-based startup builds small delivery robots used for last-mile logistics by platforms such as DoorDash and Uber Eats. Coco’s robots rely on GPS, LiDAR, and AI systems powered in part by OpenAI models to navigate dense urban environments and make route decisions in real time. Since its launch in 2020, the company has deployed robots in cities including Los Angeles, Austin, Miami and Helsinki. The expansion, however, attracted attention: in Chicago, more than 800 residents had signed a petition in late November, calling for a pause in Coco’s pilot program, citing security and accessibility concerns.
Medicine Arcadia
- Product: psychoactive drugs resulting from bioengineering
- Investment channel: personal investment/angel investor
- Investment: $9.25 million start-up in October
- Valuation: not disclosed
Arcadia Medicine is developing engineered entactogens (psychoactive compounds designed for therapeutic use) to treat conditions such as major depressive disorder, generalized anxiety disorder, and substance use disorders. The company creates modified versions of drugs including MDMA, psilocybin and ketamine, with the aim of enhancing their therapeutic benefits while reducing safety risks to meet medical and regulatory standards.
In October, the U.S. Food and Drug Administration human trials approved for Arcadia’s redesigned MDMA compound, which the company says is non-neurotoxic and allows for flexible dosing. Altman participated in the company’s $9.25 million seed round and has publicly described his work as “an important step toward a potentially transformative psychiatric treatment,” lending early credibility as Arcadia prepares for more advanced clinical trials.
Bio of the Red Queen
- Product: biosecurity
- Investment channel: OpenAI
- Investment: $15 million in fundraising in November
- Valuation: $20 to $25 million
Red Queen Bio is a biosafety startup spun out of Helix Nano, an mRNA therapeutics company that applies AI to drug development and biorisk assessment. Named after the “Red Queen Hypothesis,” which posits that species must continually adapt to survive in the face of ever-changing threats, the company aims to build safeguards for advanced AI systems at the same rate as their capabilities improve. Although Altman did not invest directly in Red Queen Bio, his prior support for Helix Nano resulted in an equity stake when OpenAI led Red Queen Bio’s November funding round, positioning the startup as part of OpenAI’s broader efforts to combat biorisks from powerful AI models.