Y Combinator (YC) is an American seed money startup accelerator launched in March 2005. It has been used to launch more than 2,000 companies, including Stripe, Airbnb, Cruise Automation, DoorDash, Coinbase, Instacart, Dropbox, Twitch, and Reddit. The combined valuation of the top YC companies was more than $300 billion by January 2021. The company’s accelerator program is in Mountain View, California. It’s considered to be one of the most successful startup incubators in Silicon Valley.