U.S. startup billion-dollar funding rounds declined during the week of September 12–18, 2026, but investors continued injecting hundreds of millions of dollars into companies working in AI infrastructure, space, investment management, and networking. Temporal Technologies topped the list with a $550 million Series E funding round, giving the company a valuation of $12.55 billion.
AI Leads Funding
Temporal Technologies develops an open-source platform for building and operating long-running AI agents and other enterprise systems. Lightspeed, Wellington Management, Goldman Sachs Alternatives, and Tiger Global led the round for the company based in Bellevue, Washington.
Factory, which specializes in AI tools for enterprise software development, ranked fifth with $200 million in funding and a valuation of $5 billion. Profound, which develops software to help companies appear more prominently in AI results, also raised $180 million in a Series D round at a valuation of $1.8 billion, led by Sequoia Capital and Kleiner Perkins.
Arcee AI, a developer of open-weight AI models, raised $150 million in a Series B round at a valuation exceeding $1 billion. The list also included Ridgeline, an AI-powered investment management platform, which raised $250 million in a Series E round at a valuation of $1.45 billion, led by founder and chairman Dave Duffield.
Space and Computing Infrastructure
Impulse Space, which develops vehicles for transporting payloads across and between orbits, raised $308 million in an extension of its Series D round. The funding brought the total size of the round to $808 million for the company based in Redondo Beach, California.
Cornelis Networks, which develops networking technologies for AI and high-performance computing workloads, closed a new $205 million funding round. Crusoe formally announced a previously reported round exceeding $3 billion, co-led by Atreides Management, Valor Equity Partners, and Mubadala Capital, but it did not enter the list’s top ten rounds.
Other Sectors Among the Largest Rounds
The rounds also included $150 million for Nex, which specializes in family-oriented digital games based on body movement rather than controllers, in a funding round combining equity and debt, and $135 million for Mazama Energy, which operates in geothermal energy from superhot rocks.
Sling Therapeutics, which is developing a small-molecule treatment for thyroid eye disease, also raised $123 million in a Series C round. The other rounds ranged from funding for AI, software, energy, and biotechnology companies, reflecting the continued concentration of capital in companies building AI infrastructure or tools around AI, alongside deep-tech fields such as space and energy.
Why Does This Matter?
The list shows that large funding amounts have not disappeared, but have become more selective compared with weeks that saw several rounds exceeding $1 billion. The presence of infrastructure, networking, and software companies among the leading positions also indicates, based on the facts included in the list, that investors are focusing not only on AI applications but also on the tools and systems required to operate them. The list alone does not reveal these companies’ performance or the detailed terms of the rounds, so funding size cannot be considered a sufficient indicator of commercial success.
Crunchbase compiled the list based on the largest announced rounds for U.S.-based companies recorded in its database during the period from September 12 to 18, 2026, with the possibility of a limited time lag in the inclusion of some rounds.