Y Combinator
About Y Combinator
Y Combinator runs a three-month program in San Francisco and invests on standard terms in every company it accepts. AI startups now make up the majority of each batch, and its AI alumni include Scale AI, Replit, Deepgram and Supabase. YC also invests in later rounds through YC Continuity. Per Crunchbase, Y Combinator has made 8,997 investments, 3,895 as lead investor across 6,899 portfolio companies, with 807 exits including 30 IPOs.
AI companies make up most recent batches, and the Lounge deals desk logs AI rounds at pre-seed, seed, Series A, Series B and Series F. Rounds marked as led include Ultra (Series A and seed, $62M, 2026-10), Ploy (seed, $27M, 2026-06) and Tolmo (seed, $22M, 2026-06). Other AI rounds on the desk include Nous Research (Series B, $90M, 2026-10), Poetiq (seed, $45.8M, 2026-01) and Supabase (Series F, $500M, 2026-07), a firm alumnus. Many pre-seed rounds from March and June 2026 are also marked as led by the firm.
The firm's public focus covers pre-seed, seed and follow-on investing, and it backs later rounds through YC Continuity. The Lounge deals desk lists a large group of pre-seed rounds at $500K each, marked as led by the firm. The firm's own check size per company is not stated in the sources reviewed for this page.
- Supabase: Series F, $500M (2026-07), a firm alumnus
- Nous Research: Series B, $90M (2026-10)
- Poetiq: seed, $45.8M (2026-01)
- Ultra: Series A and seed, $62M (2026-10), marked as led
- Ploy: seed, $27M (2026-06), marked as led
- Tolmo: seed, $22M (2026-06), marked as led
- Luel: seed, $31.2M (2026-05)
- Scale AI, Replit and Deepgram: AI alumni, no round details on the Lounge deals desk
Investing activity
Y Combinator has made 8,997 investments according to Crunchbase across 6,899 portfolio companies, and has led 3,895 rounds and seen 807 exits, 30 of them by IPO.
Y Combinator appears in 657 AI deals tracked by the AI Lounge deals desk, rounds totalling $1.05B, and led 575 of them. The rounds are mostly Pre-seed, Seed and Series A, with a median round size of $500K and the largest at $500M. The most recent are Reflex (Series A, $14M, Oct 2026), Infisical (Series B, $40M, Oct 2026) and Blacksmith (Series C, $66M, Oct 2026).
Y Combinator most often invests alongside Pioneer Fund, Transpose Platform Management, Rebel Fund and General Catalyst, and the companies it backs on AI Lounge are mostly in AI, Enterprise AI app platform and AI agent security.
Deals
Frequently asked questions about Y Combinator
Does Y Combinator invest mainly in AI startups?
AI companies make up most recent batches, and the Lounge deals desk logs AI rounds from pre-seed through Series F. Several of these rounds are marked as led by the firm.
What stages does Y Combinator invest in?
The firm's focus covers pre-seed, seed and follow-on rounds. It also invests in later rounds through YC Continuity.
Which recent AI rounds did Y Combinator lead?
The Lounge deals desk marks Ultra (Series A and seed, $62M, 2026-10), Ploy (seed, $27M, 2026-06) and Tolmo (seed, $22M, 2026-06) as led. Many pre-seed rounds from 2026 are also marked as led.
How much does Y Combinator invest in a pre-seed startup?
The sources reviewed do not publish the firm's check size. The Lounge deals desk lists several pre-seed rounds at $500K, marked as led by the firm.
Where is Y Combinator based and how long is its program?
Y Combinator is based in San Francisco and runs a three-month program. It invests on standard terms in every company it accepts.
What AI companies has Y Combinator invested in?
Y Combinator's AI investments include Reflex, Infisical, Blacksmith, Minicor, Molagri, Clueso, Lightsprint and Readily. The 657 rounds on AI Lounge are listed on this page with amounts, dates and co-investors.
Where is Y Combinator based?
Y Combinator is based in Mountain View, California, United States.
What stage does Y Combinator invest at?
In the rounds tracked on AI Lounge, Y Combinator has invested at Pre-seed, Seed, Series A and Series B, with a median round of $500K. Y Combinator led 575 of those rounds.
Who does Y Combinator co-invest with?
Y Combinator's most frequent co-investors on AI Lounge are Pioneer Fund (15 deals), Transpose Platform Management (12 deals), Rebel Fund (11 deals), General Catalyst (8 deals) and Orange Collective (6 deals).
How can founders reach Y Combinator?
Founders on AI Lounge can see Y Combinator's contact details in AI Investor Contacts (paid plans), check for a warm introduction through members who worked with the firm under Warm Paths, and add Y Combinator to their Investor Pipeline to track the conversation.