Y Combinator
Y Combinator is the Silicon Valley startup accelerator behind Airbnb, Stripe, and Coinbase. Sector-agnostic by design, it funds founders at the earliest stage on a standard deal and has dabbled in water since a 2017 call for water startups. As of 2026 it has backed 4 water companies across 7 deals.
Compiled by Antoine Walter, (don't) Waste Water, from official filings and direct intelligence in Leviathan.
The take
Y Combinator is the most famous startup accelerator in the world, the program that wrote some of the first cheques into Airbnb, Stripe, Dropbox, and Coinbase. It is sector-agnostic to the core: twice a year it backs hundreds of founders on the same terms, a standard $500,000 deal with no board seats, and lets them work out the details of what they are building later. It was founded in 2005 by Paul Graham and Jessica Livingston, and as of June 2026 it is run by President and CEO Garry Tan, himself a YC alum. Water is not a thesis here; it is one of the things ambitious founders occasionally turn up wanting to fix.
Y Combinator's water story has a real starting point, and it is not a fund memo. In January 2017 it published a Request for Startups for water, an open call for founders working on desalination, cheaper purification, smarter irrigation, anything that could make clean water abundant. That single blog post is most of the reason a generalist Silicon Valley accelerator keeps turning up in a water database at all.
Y Combinator's water footprint stays small and opportunistic: 4 water companies across 7 deals in (don't) Waste Water's Leviathan database, enough to earn a Committed water-commitment rating. The bets read like classic YC, software-first and unglamorous: Waterplan, which scores corporate water risk for buyers like Coca-Cola; Biobot Analytics, which reads public health out of sewage; and Spout, its most recent water seed. For a newcomer to water investing, the read is simple: Y Combinator is where you catch a water company at the moment it is still two founders and an idea, long before a water-focused fund would write a cheque.
Water Commitment Score
Compiled from official filings, third-party records, and direct intelligence from investors and founders, in Leviathan · recomputed monthly · as of Jun 2026.
How they invest
Portfolio · 4 water companies
Invests alongside
Highlighted = profiled on (don't) Waste Water.
Frequently asked
- What does Y Combinator invest in?
- Y Combinator invests in early-stage startups across almost every sector, from software and AI to biotech and hardware, funding founders twice a year through its accelerator. Its water bets are a small slice, four water companies including Waterplan and Biobot Analytics, rather than a dedicated water strategy.
- Does Y Combinator invest in water startups?
- Y Combinator does back water startups, though it is not a water fund. It published a public Request for Startups for water in 2017 and has since funded companies like Waterplan and Spout, four water companies across seven deals in the Leviathan database, out of thousands of investments overall.
- Who runs Y Combinator?
- Y Combinator was founded in 2005 by Paul Graham and Jessica Livingston, among others. As of June 2026 it is led by President and CEO Garry Tan, a YC alumnus, alongside group partners such as Dalton Caldwell, Michael Seibel, and Jared Friedman who run its investment program.
- Where is Y Combinator based?
- Y Combinator is based in San Francisco, California. Founded in 2005 in Cambridge, Massachusetts, the accelerator moved to Silicon Valley and now runs its batches there, funding founders worldwide on a standard $500,000 deal with no board seats.
- Is Y Combinator a company or a programming concept?
- Y Combinator the firm is a startup accelerator and venture investor in San Francisco, named after the Y combinator, a concept in theoretical computer science. The fund backs early-stage companies, including a handful of water startups, and is unrelated to the mathematical function itself.