id,date,date_precision,status,transaction_type,round,amount_usd_low,amount_usd_high,lead_or_buyer,co_leads,valuation_usd_low,valuation_usd_high,valuation_basis,valuation_to_run_rate_multiple,multiple_bound,multiple_basis,step_up_vs_prior_closed,price_per_share_usd_low,price_per_share_usd_high,shares,source,source_url,other_source_urls,notes,last_updated
series-g-2026-06-04,2026-06-04,day,Closed round,primary_equity,Series G,500000000,500000000,Thrive Capital,"With: Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, Bill Ford (new); existing investors",15500000000,15500000000,"Post-money, stated by Helion (“values the company at $15.5 billion post-money”)",,,,2.86,,,,"Helion, 4 Jun 2026 (updated Sep 2026)",https://www.helionenergy.com/newsroom/helion-raises-465-million-series-g-funding-round-to-meet-surging-global-demand-for-power,https://techcrunch.com/2026/06/04/helion-the-sam-altman-backed-fusion-startup-raises-465m-to-build-a-power-plant-for-microsoft/ https://www.geekwire.com/2026/helion-funding-round-grows-to-500m-amid-uncertainty-over-fusion-startups-microsoft-timeline/,"Helion: the oversubscribed round closed at $500M in September 2026, up from the $465M first close, and was capped. Helion: total invested to date $1.5B.",2026-11-13
series-f-2025-01-28,2025-01-28,day,Closed round,primary_equity,Series F,425000000,425000000,"Not named; participants include Sam Altman, Mithril Capital, Capricorn Investment Group, Dustin Moskovitz (Good Ventures Foundation), Nucor and SoftBank Vision Fund 2",,5425000000,5425000000,"Post-money, stated by Helion (“values the company at $5.425 billion post-money”)",,,,1.81,,,,"Helion, 28 Jan 2025",https://www.helionenergy.com/newsroom/helion-announces-425m-series-f-investment-to-scale-commercialized-fusion-power,https://techcrunch.com/2025/01/28/helion-raises-425m-to-help-build-a-fusion-reactor-for-microsoft/,TechCrunch printed $5.245B; the page uses Helion’s own figure. Helion: total invested over $1B after this round.,2026-11-13
series-e-2021-11-05,2021-11-05,day,Closed round,primary_equity,Series E,500000000,500000000,Sam Altman,"With: Dustin Moskovitz, Mithril Capital, Capricorn Investment Group",3000000000,3000000000,"Reported by Axios, via GeekWire (“valued at $3 billion”); not stated by Helion",,,,,,,,"Helion, 5 Nov 2021",https://www.helionenergy.com/newsroom/helion-raises-500m,https://www.geekwire.com/2021/interest-fusion-energy-ignites-helion-lands-500m-openai-ceo-facebook-co-founder/,GeekWire: Altman contributed $375M. The $1.7B milestone commitments are not counted in the amount.,2026-11-13