SA国际传媒

Want to keep track of the largest startup funding deals in 2025 with our curated list of $100 million-plus venture deals to U.S.-based companies? Check out The SA国际传媒 Megadeals Board.

This is a weekly feature that runs down the week鈥檚 top 10 announced funding rounds in the U.S. Check out the biggest funding rounds of last week here.

While the year started out hot for large megaround deals, it has slowed considerably. Just three startups raised nine-figure rounds this week and you barely needed a round of $60 million to make this list.

1. , $425M, energy: Fusion startup Helion Energy locked up a $425 million Series F 鈥� valuing the company at $5.4 billion 鈥� as the company looks to commercialize its fusion technology. The round included participation from investors including , 2 and . The Everett, Washington-based startup has now raised more than $1 billion. In November 2021, Helion closed a $500 million Series E. The new round further illustrates investors鈥� appetite for new energy sources as power needs increase due to AI and other advances. In 2023, Helion announced a power purchase agreement with to deliver electricity from its fusion plant starting in 2028, and a customer agreement with to develop a power plant in the 2030s. Helion has just started operating its seventh generation prototype, Polaris, which is expected to demonstrate the first electricity produced from fusion. The company鈥檚 new round is the second-largest in the fusion sector since the start of last year, per SA国际传媒 data. Last October, , a startup attempting to create a nuclear fusion-based energy source, raised more than $900 million in a Series A led by .

2. , $180M, artificial intelligence: Voice AI startup ElevenLabs raised a $180 million round led by and at a $3.3 billion valuation. The raise comes about a year after the startup locked up an $80 million Series B at a unicorn valuation. The Brooklyn-based company allows creators, enterprises and others to use AI software to replicate voices in dozens of languages. Founded in 2022, ElevenLabs has raised $281 million, .

3. , $123M, insurance: The most expensive purchase most people will ever make is their home, so it matters who insures it. Openly provides independent insurance agents with a platform that offers coverage to homeowners and streamlines processes, improves risk underwriting and helps with claims. The Boston-based insurtech startup raised $123 million in equity financing led by this week, and another $70 million in debt. In 2023, the company raised a $100 million Series D, also led by Eden Global Partners. Founded in 2017, the company has raised nearly $431 million, .

4. , $97M, biotech: Boston-based Atalanta Therapeutics, a biotechnology using RNA interference for the treatment of neurological diseases, completed a $97 million Series B co-led by and . The company will use the cash to support clinical trials of its experimental RNAi therapies for KCNT1-related epilepsy and Huntington’s disease. Founded in 2018, the company has raised $207 million, .

5. (tied) , $75M, human resources: San Francisco-based recruiting startup Mercor raised a $75 million round led by 1聽that values the company at a $2 billion valuation, per a report. The company started the process in December and the final total could still increase. Founded in 2023, the company has raised nearly $109 million, .

5. (tied) , $75M, power grid: Woburn, Massachusetts-based Veir, a developer of superconducting platforms for AI-driven data centers and utilities, closed a $75 million Series B led by . Founded in 2019, the company has raised nearly $112 million, .

7. , $70M, defense: Castelion, a defense manufacturer developing long-range hypersonic strike weapons, raised a $100 million Series A in a mix of debt and equity. The El Segundo, California-based startup creates what it calls 鈥渁ffordable, mass-produced hypersonic long-range strike weapons鈥� that serve as a 鈥渘on-nuclear deterrent.鈥� The Series A 鈥� which includes $30 million in venture debt from 鈥� was led by . Defense tech has garnered major headlines in the past several months after massive raises by the likes of and artificial intelligence defense software developer . Just late last year, defense and critical infrastructure tech startup raised $145 million in a Series B. Already this year, raised a $60 million Series C and locked up a $50 million Series B.

8. (tied) , $65M, biotech: South San Francisco-based Helicore Biopharma, a biopharmaceutical startup focused on the treatment of obesity and related conditions, emerged from stealth mode with $65 million in a Series A co-led by and .

8. (tied) , $65M, electronics: Durham, North Carolina-based Smart Wires, a company that develops solutions for a more reliable and affordable power grid, raised $65 million in a new investment that included participation from . Founded in 2010, the company has raised $248 million, .

10. , $60M, health care: San Francisco-based Rad AI, an artificial intelligence-enhanced radiology firm, locked up a $60 million round led by that values the company at $525 million. Founded in 2018, Rad AI has raised more than $140 million, per the company.

Big global deals

The largest deal outside the U.S. came from the Iberian Peninsula.

• Spain-based , an all-in-one platform for managing business travel, raised a $200 million Series E that values the company at $2.7 billion.

Methodology

We tracked the largest announced rounds in the SA国际传媒 database that were raised by U.S.-based companies for the seven-day period of Jan. 25 to Jan. 31. Although most announced rounds are represented in the database, there could be a small time lag as some rounds are reported late in the week.

Illustration: