Y Combinator is a venture capital firm that provides seed funding, mentorship, and resources to early-stage startups. The company was founded in 2005 by Paul Graham, Jessica Livingston, Trevor Blackwell, and Robert Morris, and has since funded over 2,000 startups, including Airbnb, Dropbox, and Stripe. Y Combinator's mission is to help startups succeed by providing them with the tools and resources they need to grow and scale their businesses.