United States · Series F startup
3 rounds we have observed, with the 11 investors named in them. Every figure came from a named source, and where the company reported a raise to the SEC itself, that is shown beside it.
Valuation: $5.4B, Mar 2026Y Combinator: S14
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Funding summaryUpdated 15 Nov 2026
$437Mraised across 3 rounds since 2014, from 5 sources
Each circle is a round, placed by date and sized by amount. The line above is the running total.
Y Combinator
Lightspeed Venture Partners
SoftBank
SoftBank Vision Fund
Sam Altman
Capricorn Investment
Mithril Capital Management
Good VenturesReported by Crunchbase News and 2 others
No investor was named in the report.
From a historical funding recordSEC filing: $11M sold, first sale Jun 2015
From a historical funding recordSEC filing: $1.5M sold, first sale Jul 2014
Helion Energy filed 2 raises, $12M in all. Filings say how much was sold and to how many investors; they never name the investors.
From Helion Energy's own website and the SEC filings it signed: 4 founders, 5 on the team.
On the board, as filediAjay RoyanSam Altman
The busiest backers across the latest rounds. A filled square is a round they joined; a dark one, a round they led.
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These 2 firms list Helion Energy as a portfolio company on their own websites, but no report of a round names them. They are the firms' own claims, kept apart from the rounds above.
Helion Energy's investors include Y Combinator, Mithril Capital Management, Lightspeed Venture Partners, SoftBank and SoftBank Vision Fund, and 6 more on record.
Helion Energy has raised $437M across 3 rounds since 2014.
Helion Energy's most recent round was a Series F of $425M in Jan 2025.
Its most recent round, $425M in Jan 2025, is also its largest on record.
Helion Energy's first round on record, in Aug 2014, was backed by Y Combinator and Mithril Capital Management.
Helion Energy's latest named round is a Series F, in Jan 2025.
Helion Energy is based in the United States.
In the same sector, and raised in the last eighteen months.
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United States · 
