Want to keep track of the largest startup funding deals in 2026 with our curated list of $100 million-plus venture deals to U.S.-based companies? Check out The Crunchbase Megadeals Board.
This is a weekly feature that runs down the week’s top 10 announced funding rounds in the U.S. Check out last week’s biggest funding deal roundup here.
Another week, another bevy of big rounds. For this past week, the largest round was a reported $5 billion Nvidia-backed financing for foundational AI unicorn Safe Superintelligence, followed by a $1 billion investment in Commonwealth Fusion Systems. Other sizable rounds went to companies in sectors including energy storage, health testing, nuclear power, fintech, and, yes, AI.
1. Safe Superintelligence, $5B, foundational AI: AI lab Safe Superintelligence announced a long-term partnership with Nvidia to rapidly accelerate its growth. The deal reportedly included a $5 billion investment from the chip giant with an eye toward boosting compute resources for Safe Superintelligence, a Silicon Valley startup founded by OpenAI co-founder Ilya Sutskever.
2. Commonwealth Fusion Systems, $1 billion, fusion energy: Commonwealth Fusion Systems, a startup working on fusion energy technology and developing a grid-scale fusion power plant, raised $1 billion in fresh funding from unspecified investors. The round brings the total invested to date for the Massachusetts-based company to $4 billion.
3. Antora Energy, $550M, thermal energy storage: Antora Energy, a company that provides energy through thermal batteries to data centers, announced that it has closed on $550 million in a Series C funding round. G2 Venture Partners and Eclipse co-led the financing for the nine-year-old, San Jose-based company.
4. Function, $450M, health testing: Austin-based Function, a provider of lab testing, imaging, and personal health information that markets to consumers, secured $450 million in growth financing from General Catalyst.
5. Antares, $370M, nuclear energy: Antares, a nuclear fission energy company that develops compact microreactors for defense and space applications, raised $370 million in Series C equity funding. Paradigm and Caffeinated Capital led the financing for the three-year-old company, which raised $100 million in debt funding alongside the equity investment.
6. Simile, $200M, AI simulation: Simile, a developer of AI tools for running simulations, said it picked up over $200 million in fresh funding at a $2 billion post-money valuation. Greenoaks led the round, which comes just five months after the Palo Alto-based company launched its product.
7. ThreatLocker, $190M, cybersecurity: Cybersecurity provider ThreatLocker closed on $190 million in Series F funding to hone its platform and expand internationally. Elephant led the round for the Orlando-based company.
8. CAIS, $170M, fintech: New York-based CAIS, an alternative investment platform for independent financial advisors, secured $170 million in Series D financing. Vista Equity Partners led the round, which set a valuation for the company of more than $2 billion.
9. PEX, $160M, fintech: PEX, an AI-enabled provider of prepaid and charge cards for businesses, along with tools to track finances, raised $160 in equity and debt funding, with Bluff Point Associates as lead investor.
10. Eliyan, $145M, AI infrastructure: Eliyan, a developer of connectivity technology for AI infrastructure, completed its Series C with a total of $145 million at a $1 billion valuation. Seligman Ventures led the financing for the five-year-old Santa Clara, California-based company.
Illustration: Dom Guzman
