Full-Time
Seed-stage startup accelerator and investor
$250k - $500k/yr
H1B Sponsorship Available
San Francisco, CA, USA
In Person
On-site five days/week at Dogpatch campus; relocation assistance available.
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Y Combinator is a startup accelerator that funds early-stage companies through seed investments and a three-month, batch-based program. Founders receive mentorship, guidance on product and business strategy, and a Demo Day to present to invited investors. The program runs four times a year, creating a strong network effect among participants who can support one another and share experiences. The accelerator’s portfolio spans software, fintech, biotech, and consumer products, with notable alumni including Stripe, Airbnb, and Coinbase. Unlike many investors, Y Combinator combines a small equity stake with access to a vast alumni and investor network, monetizing returns from successful exits such as acquisitions or IPOs. Its goal is to identify high-potential ventures, help them grow, and generate meaningful financial returns for its stakeholders through exits.
Company Size
1,001-5,000
Company Stage
Pre-seed
Total Funding
$48B
Headquarters
San Francisco, California
Founded
2005
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Health Insurance
Dental Insurance
Vision Insurance
Life Insurance
Disability Insurance
Health Savings Account/Flexible Spending Account
Unlimited Paid Time Off
Paid Holidays
401(k) Retirement Plan
401(k) Company Match
Parental Leave
Fertility Treatment Support
Commuter Benefits
Natalie Aresta-Katz, a Columbia Business School MBA student, has been accepted into Y Combinator's Spring 2026 batch with Regbase, an AI-powered legal research platform. She is the first current CBS student admitted to the accelerator since 2019. Aresta-Katz developed Regbase whilst working at law firm Paul, Weiss, where she tracked environmental, social, and governance disclosure laws across more than 90 countries. The platform helps companies and law firms monitor new and proposed regulations across multiple jurisdictions, including those on obscure government websites and social media. Co-founded with former Vercel engineer Ethan Shea, Regbase completed Y Combinator's three-month programme and closed an undisclosed seed round. The company has already secured clients amongst major law firms. Aresta-Katz was one of only 18 women among the batch's 431 founders.
San Francisco-based Blacksmith has raised $45 million in Series B funding led by Peak XV Partners, valuing the AI code-testing startup at $550 million. This marks a nearly tenfold increase from its $60 million valuation when it secured $10 million in Series A funding less than a year ago. Founded in 2024, Blacksmith helps companies build, test, and verify software. The startup now serves over 5,000 customers, including Mercury, Supabase, and Expensify, up from 700 customers a year ago. Co-founder and CEO Aditya Jayaprakash said the company reached $10 million in annualised revenue with just 10 employees. Revenue has since grown to "tens of millions of dollars" with a 30-person team. Blacksmith faces competition from GitHub Actions, Cursor Automations, and testing services from Amazon Web Services, Microsoft Azure, and Google Cloud.
River Markets announced Tuesday it raised $8.5 million in a seed round led by Haun Ventures. Y Combinator and Coinbase Ventures also participated in the fundraise, which closed in July. The startup provides a platform that allows professional traders to trade across multiple prediction markets from a single interface. Co-founded by CEO Oscar Levy and CTO Antonin Parrot, River Markets launched in May and is on track to exceed hundreds of millions of dollars in annualised trading volume by year-end. The funding will be used to hire engineers, build faster trading systems, and expand sales and operations teams. The announcement reflects growing institutional interest in prediction markets as financial tools for hedging risks and trading on economic events.
Axle, an AI-native insurance clearinghouse, has raised $17.5 million in Series A funding led by Base10 Partners. Y Combinator and Gradient continued their investment, with participation from Stage 2 Capital and industry angels. The company now clears more than $100 billion in coverage annually for over 4,000 clients, including Fortune 500 customers such as Rocket Mortgage, Avis, Experian, and Sonic Automotive. Axle has accelerated insurance verification workflows by 20 times whilst helping customers recover hundreds of millions in losses. Axle addresses inefficiencies in the $8.3 trillion insurance industry, which still relies heavily on manual processes like faxes and phone calls. The company's infrastructure integrates fragmented carrier systems into a single API. The fresh capital will fund expansion into more than 50 insurance segments and deepen carrier relationships.
River AI, founded by xAI co-founder Igor Babuschkin, has raised $1.1 billion in funding led by General Catalyst and AMP PBC. The round includes strategic investments from NVIDIA and AMD Ventures, with additional backing from Y Combinator and Temasek. The Palo Alto-based company offers an API that enables enterprises to complete complex reinforcement learning training runs in 15 to 20 minutes without requiring an infrastructure team, at two to four times the cost savings versus closed-source alternatives. River AI's platform provides state-of-the-art LoRA fine-tuning and reinforcement learning for frontier open weight models. The company aims to make AI ownership accessible to developers and organisations rather than relying solely on general-purpose models. Babuschkin previously worked at Google DeepMind and OpenAI before co-founding xAI.