Helion, the fusion startup backed by Sam Altman, announced on Thursday that it had raised $465 million in a new funding round that values the company at $15.5 billion.
The cash infusion lands as Helion is racing to complete Orion, its first power plant. The startup has set an aggressive timeline to deploy fusion power to the grid, as early as 2028 if it can deliver on the terms of its deal with Microsoft.
The startup last raised $425 million in January 2025. Altogether, Helion said it has raised $1.5 billion.
The new round, a Series G, was led by Thrive Capital with a long list of participants, including new investors Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford, along with existing investors, which include Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Dustin Moskovitz through Good Ventures Foundation, SoftBank Vision Fund 2, and a university endowment fund.
Helion’s approach to fusion power differs from many of its peers. Some use magnets to contain the superheated plasma required for fusion conditions, while others use lasers to compress fusion fuel until it reacts. In both cases, the majority of startups plan to use steam turbines to transform the intense heat into electricity.
