October 2026's Biggest US Startup Funding Rounds: OpenAI's $11B Leads 9 Tracked Deals

OpenAI's $11 billion round, which valued the company at roughly $1.25 trillion after it fell short of a $30 billion target, was the biggest US startup funding round Value Add VC tracked for October 2026 as of November 6, 2026 — leading a group of 308 tracked rounds worth $50.0 billion combined.

These are rounds tracked by Value Add VC for US and unconfirmed-HQ private companies, as of November 6, 2026; rumored rounds, public-company raises, and known non-US companies are excluded. This is not a US market total — it's a slice of the market from the sources Value Add VC follows, meant to be compared month to month within this series rather than against PitchBook, Crunchbase, or other trackers' totals. Below are the 9 biggest qualifying rounds, ranked, each linked to its own source.

Biggest Startup Funding Rounds October 2026: The Full List, Ranked by Size

Tracked as of November 6, 2026, OpenAI's $11 billion round tops October 2026's list, followed by Re:Build's $2.1 billion raise and Axiom Solutions' $2 billion convertible-preferred financing. Three of the nine rows — OpenAI, Flapping Airplanes, and TypeSafe AI — are tagged AI & Infrastructure in Value Add VC's intelligence store.

Computed from the Value Add VC intelligence store on 2026-11-06: funding rounds of US and unconfirmed-HQ private companies announced in October 2026; rumored rounds, public-company raises, and known non-US companies excluded; one record per deal. Not a market total; each company name links its own source. How we counted: rounds Value Add VC's intelligence store had on file for October 2026; ranked by disclosed round size; 9 of 308 tracked deals; as of November 6, 2026.

What Was the Biggest Startup Funding Round in October 2026?

OpenAI's roughly $11 billion round, reported by the Wall Street Journal and republished October 31, 2026, closed at less than half of the $30 billion the company had reportedly been targeting, as some large prospective backers pulled back from committing more capital. The round still valued OpenAI at roughly $1.25 trillion — short of the $1.4 trillion the company had been aiming for, but still the largest round Value Add VC tracked for the month by a wide margin.

The second- and third-place rounds both went to industrial rather than AI-model companies: Re:Build's $2.1 billion raise, announced October 27, 2026 and co-led by General Catalyst and JPMorganChase's Strategic Investment Group, went to the manufacturing holding company that previously spun out electric-truck maker Slate Auto. Axiom Solutions' $2 billion convertible-preferred financing, announced October 5, 2026 and co-led by General Catalyst and Koch Equity Development, set an initial enterprise value of $37.5 billion — an enterprise value rather than a traditional post-money valuation, and still subject to customary regulatory approvals and closing conditions as of that announcement.

Which Investors Were Most Active in October 2026's Biggest Rounds?

General Catalyst was the only firm to appear more than once across the 9 biggest rounds tracked as of November 6, 2026: it co-led Re:Build's $2.1 billion raise alongside JPMorganChase's Strategic Investment Group, and separately co-led Axiom Solutions' $2 billion financing alongside Koch Equity Development. Index Ventures and Lux Capital co-led Flapping Airplanes' $1 billion Series A, a round for a one-year-old AI lab reportedly valued at $6 billion, according to Bloomberg.

Three of the nine rounds went to AI-infrastructure-adjacent companies outside the frontier labs: TypeSafe AI raised an $870 million Series A led by Andreessen Horowitz at a $7.5 billion valuation, detailed further in TypeSafe AI's valuation deep dive; Modal Labs raised $750 million led by Accel (joined by Kleiner Perkins) at a $15.75 billion valuation, more than triple its level after a May 2026 round, covered in Modal Labs' valuation history; and FuriosaAI raised a $620 million Series D at a $2.9 billion valuation to build energy-efficient inference chips, detailed in FuriosaAI's valuation deep dive.

How We Built This List

This ranking covers US and unconfirmed-HQ-private-company funding rounds in the Value Add VC intelligence store that were announced in October 2026, with one record kept per deal. It excludes rumored rounds, public-company capital raises, and companies with a confirmed non-US headquarters. The store tracked 308 such rounds worth roughly $50.0 billion combined as of November 6, 2026 — a slice of the market from the sources Value Add VC follows, not a claim to cover every round that closed in October.

Every row above is checked against its own linked source. One exception: Ramp's source returned an access error on re-check, so that row's figures are kept as tracked and attributed to the PR Newswire release carried by Morningstar rather than independently re-verified here. Kalshi's source, a paywalled briefing from The Information, confirmed the $1 billion amount and $40 billion valuation but not the exact date or round letter, so those two fields are kept as tracked and attributed to The Information.

A 10th deal the store had flagged for October 2026, a $10 billion vehicle announced by the firm Disruptive on October 27, 2026, is left out of this list entirely: on re-check, that capital is a blind-pool fund the firm raised from its own limited partners to make growth-stage bets, not a startup raising capital, so it falls outside this list's own definition of a funding round.

The full round-level log this list draws from is public at Value Add VC's funding tracker, and October's rounds are ranked alongside the full year to date in 2026's top US startup funding rounds so far and against the prior month's tracked total in September 2026's biggest US startup funding rounds, as tracked as of November 6, 2026.

What the headline misses

A ranked list by round size flattens very different kinds of capital events into one table. OpenAI's shortfall against its own $30 billion target is itself a data point about investor appetite, not just a funding milestone — the same large backers who wrote nine- and ten-figure checks earlier in 2026 pulled back here. Axiom Solutions' $37.5 billion figure is an enterprise value tied to a deal still subject to regulatory approval at announcement, not a closed, disclosed post-money valuation, and two rows (Ramp and Kalshi) rest on sources this research could not independently re-open, so their figures are attributed to the outlets that reported them rather than verified firsthand here.