- Small Follow-on OfferingUSD 75M — Amount basis: USD 75M; Post-money valuation: Approx. USD 852B; Led by: Glynn Capital | A small follow-on after Series G, amount only USD 75M, maintaining valuation at approx. USD 852B. | Source: Aggregated public reports
- SeriesGUSD 122B — Amount: USD 122B; Post-money valuation: USD 852B; Led by Amazon (USD 50B) | The largest single private financing round in human history. At announcement on 2026-02-27, pre-money valuation was USD 730B with a target raise of USD 110B; final closing on 2026-03-31 at USD 122B raised, resulting in a post-money valuation of USD 852B. Amazon anchored the round with USD 50B (corresponding to AWS compute binding), NVIDIA contributed USD 30B continuing the 'supplier investing in customer' model, and SoftBank contributed USD 30B. This round briefly made OpenAI the most valuable private company globally (later surpassed by Anthropic's USD 965B valuation in May 2026). | Source: OpenAI Official Announcement (2026-02-27)
- Small-Scale Follow-on OfferingUSD 1B — Amount basis: Approx. USD 1B; Post-money valuation: USD 500B; Led by: Undisclosed | Small-scale additional issuance of approx. USD 1B, maintaining valuation at USD 500B. Investors were not publicly disclosed. | Source: Aggregated public reports
- PBC Restructuring + Employee Secondary Share LiquidityUndisclosed — Amount: approx. USD 10B (secondary shares); approx. USD 10B; Post-money valuation: USD 500B; Participated by existing investors | Two events overlapped: ① The capped-profit structure was formally abolished, changing to a standard equity structure for OpenAI Group PBC; the non-profit OpenAI Foundation retained strategic control and held approx. 26% directly, Microsoft held approx. 27% (corresponding to approx. USD 135B market cap); ② Employee secondary sale of approx. USD 10B, anchoring valuation at USD 500B. This is a key step for OpenAI moving from a 'special structure' to an 'IPO-ready structure'. | Source: OpenAI Official Announcement (Oct 2025)
- SeriesFUSD 40B — Amount: $40B; Post-money valuation: $300B; Led by: SoftBank Group | SoftBank led approximately $30B of the round; the single-round $40B set a then-private market record, with a post-money valuation of $300B—up from $157B six months earlier. SoftBank's condition required OpenAI to complete its for-profit restructuring by the end of 2025, directly driving the PBC conversion in Oct 2025. | Source: OpenAI Official Announcement (Mar 2025)
- SeriesFUSD 6.6B — Amount scope: USD 6.6B; Post-money valuation: USD 157B; Led by: Thrive Capital | Valuation jumped from USD 29B to USD 157B (~5.4x), led by Thrive Capital. NVIDIA's first equity stake is symbolic—compute suppliers began binding core customers via equity, a model amplified to the USD 30B scale in the 2026 Series G. | Source: OpenAI Official Announcement (Oct 2024)
- Convertible Bonds and Debt FinancingUSD 4B — Amount: USD 4B; Post-money valuation: N/A (debt); Led by: Banking Consortium | USD 4B revolving credit facility provided by a syndicate of 10 banks. This is OpenAI's first large-scale use of debt instruments, reflecting its capital structure evolving from pure equity to an 'equity + debt' hybrid. | Source: Public Report Summary
- Series E Secondary Share TransferUndisclosed — Amount: Approx. USD 300M; Post-money valuation: USD 27B–29B; Led by Sequoia Capital | Transfer of old shares from employees and early investors, rather than new share issuance by the company—this marks the first time traditional VCs gained exposure to OpenAI through secondary markets, with a valuation range of USD 27B-29B. | Source: Aggregated Public Reports
- Microsoft Strategic Investment IIUSD 10B — Amount: USD 10B (multi-year commitment); $10B; Post-money valuation: USD 29B; Led by Microsoft. Five days after ChatGPT's release on Nov 30, 2022, it reached 1 million users, breaking 100 million in two months. Microsoft subsequently announced a new multi-year, billions-of-dollars-scale investment (reported as approx. USD 10B), with a post-money valuation of USD 29B. This investment included not just capital but also Azure compute supply and product integration with Bing/Office/GitHub Copilot — Microsoft deeply bound OpenAI through a triple approach of "capital + compute + distribution." | Source: Microsoft official announcement (Jan 23, 2023)
- Microsoft Follow-on and Multiple ExtensionsUSD 1B — Amount: $1B+; Post-money valuation: ~$14B; Led by: Microsoft | Microsoft added to its initial $1B investment from 2019, bringing the post-money valuation to ~$14B. The full list of investors for this round has not been disclosed. | Source: Public reports summary
- Microsoft Strategic InvestmentUSD 1B — Amount: USD 1B; Post-money valuation: Undisclosed (reports of approx. USD 20B are rumored, officially unconfirmed); Led by: Microsoft | A milestone turning point: On March 11, 2019, OpenAI established OpenAI LP, adopting a capped-profit structure—investors can receive returns but with a cap, and excess profits flow back to the non-profit parent. This design enabled large-scale external financing, prompting Microsoft to immediately invest USD 1B while locking Azure as the exclusive cloud provider. This formed the legal and commercial basis for all subsequent financings. | Source: OpenAI Official Announcement (July 22, 2019)
- YC Seed and Early DonationUSD 80M — Amount: ~$80M; Led by: Y Combinator | At this stage, OpenAI remained a non-profit entity, with funds entering as donations/research grants, totaling ~$210M received. Elon Musk left the board in 2018 due to conflicts of interest with Tesla. | Source: Public reports summary
- Founding Donation PledgeUSD 1B — Amount: USD 1B (committed); USD 1B (committed, actual receipt approx. USD 130M); Post-money valuation: N/A (non-profit); Led by Sam Altman / Elon Musk / Peter Thiel | OpenAI appeared as a non-profit research institution, with founding donors committing USD 1B. The company explicitly stated it would only use a small portion of this in the first few years—making it completely different from regular seed rounds, with actual funds received around USD 130M. This is the starting point for understanding all subsequent "valuations" of OpenAI: there was no equity pricing benchmark in the early days. | Source: OpenAI official establishment announcement (2015-12-11)
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