NeuralStackCybersecurity startups Island and Cyera topped the week’s biggest U.S. startup funding rounds, each announcing $400 million financings. Their deals led a group of large raises spanning foundational AI, drug discovery, neurotechnology, wireless communications, and other specialized markets. The funding activity covered the period from Sept. 19 through Sept. 25, 2026, according to the source article’s methodology.
Island raised $400 million in Series F financing in a round led by Evolution Equity Partners. The Dallas-based company develops tools for secure enterprise digital operations, and the financing set its valuation at $6.4 billion, more than twice its 2024 valuation.
Cyera also secured $400 million, through a Series G extension led by Evolution Equity Partners and backed by Goldman Sachs Growth Equity. The New York-based company provides enterprise data security tools designed to govern activity involving both humans and AI agents. The round brings Cyera’s total funding to $2.7 billion, according to Crunchbase data.
Snorkel AI ranked third with a $350 million Series E round led by Insight Partners and S32. The San Francisco company develops tools that help frontier labs and AI teams create specialized training data and environments. The financing valued the seven-year-old company at $3.2 billion, and the company now reports more than $375 million in annual recurring revenue.
AI also featured in Enveda’s $311 million Series E financing. The Boulder, Colorado-based startup uses AI for drug discovery, and the round, led by Catalio Capital Management, takes its total capital raised since inception to more than $845 million. Precision Neuroscience added another major health technology deal, raising $250 million in Series D funding from lead investors Pershing Square and the Ackman Oxman Institute.
Other large rounds broadened the week’s funding landscape. Hubble Network raised $200 million in Series C financing led by Smith Point Capital, giving the Seattle company a $1.6 billion valuation for its satellite network that extends connectivity to Bluetooth devices. Rightway raised $155 million in Series E funding led by Francisco Partners and plans to use part of the financing to expand its AI capabilities.
Three companies tied at $100 million. Rainmaker, based in El Segundo, California, raised Series B funding for atmospheric research and efforts to produce new freshwater through cloud seeding. San Francisco-based Numeral closed a Series C led by Insight Partners for its AI-powered sales tax compliance platform. Micro1, also based in San Francisco, reportedly raised more than $100 million at a $4 billion valuation for its AI training-data business, according to a Forbes article cited in the source.
Why this matters
The week’s largest financings show how investment is clustering around infrastructure and tools that support the expanding use of AI. Island and Cyera are focused on enterprise security, with Cyera explicitly addressing governance for AI agents, while Snorkel AI and Micro1 supply data and development tools for AI laboratories. The scale of these rounds indicates that investors are backing both the protection and production layers of the AI economy.
At the same time, the presence of Enveda, Precision Neuroscience, Rightway, Hubble Network, Rainmaker, and Numeral demonstrates that large startup financings are not limited to a single technology category. Capital is also flowing toward applications in drug discovery, brain-computer interfaces, healthcare navigation, connectivity, climate-related research, and tax administration. Future funding rankings will show whether this broad interest persists or whether security and AI continue to pull an even larger share of major rounds.