Y Combinator AI portfolio in San Francisco

The most prolific seed accelerator in the world, batch class twice a year. Filtered to AI companies headquartered in San Francisco.

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Built from a search like: “Y Combinator-backed AI companies in San Francisco”

Ranked by current headcount across Y Combinator-backed AI companies in San Francisco. Refreshed daily.

1
OpenAI· San Francisco, California, United States
OpenAI is an AI research and deployment company dedicated to ensuring that general-purpose artificial intelligence benefits all of humanity. AI is an extremely powerful tool that must be created with safety and human needs at its core. OpenAI is dedicated to putting that alignment of interests first — ahead of profit.To achieve our mission, we must encompass and value the many different perspectives, voices, and experiences that form the full spectrum of humanity. Our investment in diversity, equity, and inclusion is ongoing, executed through a wide range of initiatives, and championed and supported by leadership.At OpenAI, we believe artificial intelligence has the potential to help people solve immense global challenges, and we want the upside of AI to be widely shared. Join us in shaping the future of technology.
- Series unknown
- 10.5k employees
- Founded 2015
2
Miracle· San Francisco, California, United States
Pulling your hair out in clinical trials because of spreadsheet madness?You’re not alone. Most biotech teams lose weeks, if not months, to manual spreadsheet trackers, delayed insights, and inadequate vendor oversight.That’s exactly why we built Miracle.👉 Speed: Replace clunky manual trackers with an integrated platform that gets you live in just days (not weeks or months).👉 Clarity: Real-time visibility across trials, so your execs stop asking you for “one quick update” every day.👉 Proof: Clinical-stage biotechs using Miracle have already finished 3-4 months ahead of trial timelines, freeing their teams from spreadsheet hell and resolving risks as soon as they occur, not next week.If you’re a biotech exec staring down another delayed trial (or want to start your study on the right foot), Miracle can help you close the gap.📩 Message us here or reach out at https://www.miracleml.com/contactLet’s make “trial delays” something you don’t talk about next quarter.
- Seed
- 73 employees
- Founded 2022
3
Culture Biosciences· South San Francisco, California, United States
Culture is your bioreactor lab, in the cloud.We help scientists accelerate bioprocess development with our high-throughput bioreactor cloud lab. You design your experiment, and we execute the experiment in our lab using our 250mL bioreactors. We take care of the high-quality execution so that you can focus on developing processes. While your experiment runs in our lab, you can monitor and analyze your data in real time using our online dashboard. With Culture, get faster insights to make better, data-driven decisions.
- Series C
- 67 employees
- Founded 2016
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4
ZBiotics· San Francisco, California, United States
Zack Abbott, PhD microbiologist, founded ZBiotics because of the potential genetically engineered probiotics have to improve daily living. Our first product is a probiotic that helps you feel better the day after drinking alcohol. ZBiotics is leveraging its patented technology to create a whole new category of products that help our bodies deal with whatever modern life throws our way. It’s genetic engineering as it should be: transparent, responsible, and people first.
- Secondary
- 63 employees
- Founded 2016
5
Elpha· San Francisco, Minnesota, United States
Elpha (YC19) is the professional network dedicated to helping high-achieving women in tech succeed at work. Our 100,000+ members come to Elpha for support, to explore new opportunities, and to make friends. We're also a startup founded and built by women.If you'd like to get to know more women in your field, apply to become a member at elpha.com
- Seed
- 43 employees
- Founded 2019

6
Invert· San Francisco, California, United States
Invert is software that connects, structures, and activates your bioprocess data using AI to give development and manufacturing teams the clarity they need to move from experiment to milestone faster.
- Seed
- 41 employees
- Founded 2021
7
Metis (Acquired by DoorDash)· San Francisco, California, United States
We build infrastructure enabling AI agents to reliably perform complex digital work tasks.
- Pre-seed
- 39 employees
- Founded 2025
8
Shasqi· San Francisco, California, United States
Shasqi is a biotech company whose mission is to revolutionize cancer treatment with click chemistry, a 2022 Nobel Prize winning technology. Our unique CAPAC® (Click Activated Protodrugs Against Cancer) platform uses click chemistry to target high doses of cancer drugs directly to the site of the tumor while minimizing toxicity to healthy cells, potentially improving the therapeutic index.Shasqi has developed an expansive and diverse library of antibody-mediated tumor-targeting agents and cancer therapeutic payloads. These are decoupled from each other and reunited at the site of the tumor via a click chemistry reaction. We are the first company to use click chemistry in humans.For more information, visit us at www.shasqi.com
- Grant
- 28 employees
- Founded 2015
9
Verge Labs· San Francisco, California, United States
Verge Labs is a frontier AI lab building world models of human disease biology. Founded in 2015 and headquartered in San Francisco, Verge develops AI models trained on proprietary multimodal human tissue data to power target discovery, in-silico validation, patient stratification, indication prioritization, and biomarker prediction. Verge partners with pharmaceutical and biotech companies to accelerate the development of treatments for CNS diseases and other complex human conditions.Verge actively seeks a diverse applicant pool in order to build the strongest possible workforce. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.
- Series C
- 27 employees
- Founded 2015
10
Cactus (YC S25)· San Francisco, California, United States
Low-latency AI engine for mobile devices & wearables.
- Pre-seed
- 25 employees
- Founded 2025

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Y Combinator-backed AI companies in San Francisco

The list above ranks Y Combinator-backed AI companies headquartered in San Francisco by current headcount, drawn from public LinkedIn and Crunchbase records. With 45 matching companies in Refolk’s index, you can see exactly where Y Combinator’s AI thesis has landed in San Francisco.

Three filters - investor, industry, city - narrow the field to a tight cluster of operators with overlapping incentives. They share a thesis, a network, and a market. Hiring from this list usually means hiring someone already inside the Y Combinator AI world in San Francisco.

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How this list is built

Refolk pulled AI companies headquartered in San Francisco whose disclosed Crunchbase investor list includes Y Combinator, ranked them by current employee count, and kept those with at least 3 employees. The list refreshes once a day.

Last refreshed: Wed, 05 Aug 2026 21:28:53 GMT

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