Define Ventures
About Define Ventures
Define Ventures is based in San Francisco and was founded by Lynne Chou O'Keefe, a former Kleiner Perkins partner who serves as founder and managing partner. Sources disagree on the founding year: PitchBook says 2019 and CB Insights says 2018. Other people listed at the firm include Chuka Esiobu (principal), Michael Wert (partner), Agneta Breitenstein (venture partner) and Hong Truong (principal). Fund I has a 2020 vintage per PitchBook, and in April 2023 the firm announced $460 million across Fund III and an Opportunities Fund that supports companies already in its portfolio. The firm says it manages six funds with about $800 million in assets.
The firm's stated focus is digital health, but CB Insights describes its scope as including AI and machine learning tools for clinical care. Its AI-related holdings include Hyro, which provides a conversational AI platform that automates tasks such as patient record identification and appointment scheduling. Lounge's deals desk also tracks a $11 million Series A in Readily, closed in October 2026. Public sources do not name the partners who lead the firm's AI deals.
The firm invests from incubation through seed, Series A and Series B. For Fund I, PitchBook lists a target of 15 to 18 investments of $0.75 million to $6 million per company. Check sizes for Fund III and the Opportunities Fund are not public.
- Readily: AI company; Series A of $11 million, October 2026 (Lounge deals desk)
- Hyro: conversational AI platform for healthcare tasks such as patient record identification and scheduling; round and year not confirmed in public sources
- definevc.com/about-us
- definevc.com/insights/define-ventures-fund-iii-and-opportunities-fund
- pitchbook.com/profiles/investor/234355-06
- pitchbook.com/profiles/fund/16486-57F
- cbinsights.com/investor/define-ventures
- crunchbase.com/organization/define-ventures
- superscout.co/investor/define-ventures
- fiercehealthcare.com/digital-health/define-ventures-raises-460m-invest
Investing activity
Define Ventures appears in 1 AI deal tracked by the AI Lounge deals desk, rounds totalling $11M, and led 1 of them. The rounds are mostly Series A, with a median round size of $11M. The most recent is Readily (Series A, $11M, Oct 2026).
Define Ventures most often invests alongside California Health Care Foundation Innovation Fund and Y Combinator, and the companies it backs on AI Lounge are mostly in Healthcare compliance AI.
Deals
Frequently asked questions about Define Ventures
Does Define Ventures invest in AI startups?
Yes, in part. Its core focus is digital health, and it has backed AI-driven companies such as Hyro and Readily. Public sources do not describe an AI-specific fund.
What stages does Define Ventures invest in?
The firm invests in incubation, seed, Series A and Series B companies. The Lounge listing also tags pre-seed.
How much capital has Define Ventures raised?
The firm announced $460 million across Fund III and an Opportunities Fund in April 2023. It says it manages about $800 million across six funds.
What check size does Define Ventures write?
For Fund I, PitchBook lists $0.75 million to $6 million per company. Current check sizes are not public.
When was Define Ventures founded and who started it?
Define Ventures is based in San Francisco and was founded by Lynne Chou O'Keefe. PitchBook gives 2019 as the founding year, while CB Insights gives 2018.
What AI companies has Define Ventures invested in?
Define Ventures's AI investments include Readily. The 1 round on AI Lounge are listed on this page with amounts, dates and co-investors.
Where is Define Ventures based?
Define Ventures is based in San Francisco, California, United States.
What stage does Define Ventures invest at?
In the rounds tracked on AI Lounge, Define Ventures has invested at Series A, with a median round of $11M. Define Ventures led 1 of those rounds.
Who does Define Ventures co-invest with?
Define Ventures's most frequent co-investors on AI Lounge are California Health Care Foundation Innovation Fund (1 deal) and Y Combinator (1 deal).
How can founders reach Define Ventures?
Founders on AI Lounge can see Define Ventures'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 Define Ventures to their Investor Pipeline to track the conversation.