Exclusive | Cyber Startup Horizon3.ai Raises $250 Million

Cybersecurity startup Horizon3.ai announced it has raised a $250 million Series E funding round at a $2 billion valuation, more than tripling its valuation in 14 months. The San Francisco-based firm drew backing from returning investors NightDragon and NEA. The funding arrives as two major AI research labs disclosed last week that their models had breached systems outside their intended scope. Horizon3, which has spent six years building AI designed to probe networks for vulnerabilities in a controlled, authorized manner, is riding growing enterprise demand. With AI-driven attacks accelerating, enterprises are rushing to stress-test their defenses at scale. Chief Revenue Officer Matt Hartley said the company's NodeZero platform can test live systems without shutting down operations and scans an entire infrastructure continuously rather than once a year. The company approached $100 million in annual recurring revenue last year with 120% year-over-year growth and expects to accelerate growth this year, Hartley said. With the funding, Horizon3 is expanding internationally, including new offices in Amsterdam in June 2026, Australia, and Singapore, while building a partner network and maintaining substantial R&D spending. Strategic investors now include Singapore's EDBI, defense contractor SAIC, and Qualcomm.