Besides being a household name with the success of ChatGPT in 2022, OpenAI CEO Sam Altman has long been one of the most influential early stage investors in Silicon Valley. Long before productive AI captured the world’s attention, Altman made a name for himself as a bettor angel investor who helped shape the modern landscape of technology, from early stakes in Stripe, Reddit and Instacart to later, aggressive investments in nuclear power and longevity science.
Altman’s background as an early-stage investor was formed during his time at Y Combinator, where he served as president from 2014 to 2019. In that role, he helped oversee investments in hundreds of startups, many of which have gone on to become major technology companies. After leaving YC, Altman continued to invest personally in both alumni companies and startups.
Over the years, Altman has invested in more than 400 companies through a combination of personal angel checks, his own funds such as Hydrazine Capital and Apollo Projects, and partnerships with major venture firms.
Altman’s investment portfolio for 2025 is focused on AI-driven security startups, biotechnology and nuclear fusion, according to Crunchbase data. This bet shows not only the desire to diversify in all high-level industries, but also to strive for “moonshot” businesses that face today’s complex challenges, from increasing creativity and clean energy to success in human life.
Here are the startups Altman has invested in this year:
Helion Power
- Product: fusion power
- Investment channel: personal/angel investment
- 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 zero-carbon energy source. The company is building its first fusion power plant in Chelan County, Wash. it is scheduled to come online in 2028. As data centers and advanced AI systems drive increased demand for electricity, interest in renewable, zero-emission energy has grown across the technology industry. Helion is positioning itself to meet that demand with a patented flexible, non-disruptive hybrid approach designed to generate electricity directly, without relying on conventional turbines. Altman has been one of the company’s most prominent proponents for several years, calling Helion 2021 “the most promising merger I’ve ever seen.” His latest investment came as part of Helion’s $425 million Series F round in January.
MirrorTab
- Product: web security technology
- Investment channel: Altman Capital
- Investment: $8.5 million seed round in February
- Rating: not disclosed
MirrorTab develops browser-based security tools that protect customer-facing web applications from threats including malware, automated fraud, sophisticated bots and so-called Agent 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 are focused on mastering AI—very few are working to limit it,” CEO and founder Brian Silverstein said at a recent conference. “Effective AI security requires knowing when to use AI and when to block it completely.”
The compass
- Product: Online education services
- Investment channel: personal/angel investment
- Investment: $46 million Series B in March
- Value: $100 million
The campus is an online, two-year college offering affordable accredited degrees taught by professors from institutions including Stanford, Princeton, and Howard University. Students attend live online classes and supplement courses with AI-generated educational tools developed by Sizzle AI The school currently offers associate degrees in business administration and information technology, with an optional focus on applied AI focused on business use cases. Altman backed Campus with its $46 million Series B round, along with investors like Figma CEO Dylan Field, Palantir founder Joe Lonsdale and Shaquille O’Neal. Altman also helps fund the company’s Shaq Scholars Program, which provides financial support to enrolled students.
ConductorAI
- Product: automation software
- Investment channel: Altman Capital
- Investment: $15 million Series A in April
- Rating: not disclosed
Founded by former Palantir employees, ConductorAI specializes in automating complex government approval and compliance workflows. The company’s software, contracted by the US Air Force, Space Force and the Office of the Secretary of Defense, uses AI to update dozens of policy and regulatory documents. In accordance with Business InsiderConductorAI has been used primarily to automate security classification, with additional applications for export licensing, International Traffic in Arms compliance and document review.
Exowatt
- Product: renewable energy
- Investment Channel: angel investing
- Investment: $70 million Series A in April and $50 million in November
- Current value: $140 million
Exowatt builds power systems designed to deliver large, on-demand power. Its technology uses Fresnel lenses to focus sunlight into heat energy, which is stored in clay bricks that act as batteries for the system’s engine and power generator. While the basic approach isn’t new, Exowatt is betting that the new capital—from Altman, venture capital firm Andreessen Horowitz and investors including Leonardo DiCaprio—will allow it to build and roll out systems domestically at speed. The goal is to provide data centers facing high demand for round-the-clock power that is cheap, reliable and low-carbon.
Coco Robotics
- Product: delivery robots
- Investment channel: personal/angel investment
- Investment: $80 million Series B in June
- Value: $300 million
Altman was the 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 deliveries by platforms including DoorDash and Uber Eats. Coco’s robots rely on GPS, LiDAR cameras and AI systems powered in part by OpenAI models to navigate dense urban environments and make real-time route decisions. Since launching in 2020, the company has deployed robots in cities including Los Angeles, Austin, Miami and Helsinki. The expansion has drawn scrutiny, however: in Chicago, more than 800 residents had signed a petition in late November calling for a pause in Coco’s pilot program, citing safety and accessibility concerns.
Arcadia Medicine
- Product: Bioengineered psychoactive drugs
- Investment channel: personal/angel investment
- Investment: $9.25 million seed round in October
- Rating: not disclosed
Arcadia Medicine develops entactogens—psychoactive compounds designed for therapeutic use—to treat conditions such as major depression, generalized anxiety disorder and substance use disorders. The company creates modified versions of drugs including MDMA, psilocybin and ketamine, aimed at enhancing their therapeutic benefits while reducing safety risks to meet medical and regulatory standards.
In October, the US Food and Drug Administration approved human testing of 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 its work as “an important step toward a potentially mind-altering treatment,” lending early credibility as Arcadia prepares for more advanced clinical trials.
Red Queen Bio
- Product: biosecurity
- Investment channel: OpenAI
- Investment: $ 15 million seed round in November
- Value: $20 million–$25 million
Red Queen Bio is a biosecurity startup that emerged from Helix Nano, an mRNA therapeutics company that uses AI in drug development and biological risk assessment. Dubbed the “Red Queen hypothesis,” which posits that species must continue to adapt to survive against changing threats, the company aims to build defenses for advanced AI systems at the same pace as their capabilities improve. Although Altman did not directly invest in Red Queen Bio, his previous support of Helix Nano led to an equity stake when OpenAI led Red Queen Bio’s November seed round, positioning the startup as part of OpenAI’s broader effort to address biological risks tied to powerful AI models.
