Horizon3 raises $250M, valuation jumps to $2B

Horizon3 closed a $250 million Series E round, raising its valuation from $650 million to $2 billion after a year of growth since June 2025. The funding was co-led by existing investors NightDragon and NEA and included seven new investors and five returning backers.

Founded in 2019, Horizon3 develops AI-driven cybersecurity software that deploys autonomous agents inside customer networks. Those agents simulate attacker behavior to locate vulnerabilities and provide step-by-step remediation guidance.

The company serves more than 7,000 customers across sectors including multinational banking and healthcare and counts four Fortune 10 firms among its clients. Horizon3 reported 120% year-over-year growth in annual recurring revenue, a performance metric investors cited when committing capital.

Horizon3 said the Series E proceeds will go primarily toward go-to-market expansion and product research. The company plans to scale partnerships with managed service providers and telecommunications firms to increase distribution and capacity to serve those channels.

Matt Hartley, chief revenue officer, noted, “Building the capacity to get out and service those various markets through those paths to market is a top priority for use of the funds we raise.” He added, “AI attacks and innovation in AI never stops. The AI threat grows hourly, if not by every minute, for the customer market.”

Investors pointed to the size of the addressable market and Horizon3’s recent customer and revenue growth as reasons for backing the round.