Marc Andreessen is the co-founder and general partner of Andreessen Horowitz (a16z), one of the most influential venture capital firms in the world.

Before he was an investor, he was a builder. At 22, Andreessen co-created Mosaic, the first widely used graphical web browser, then co-founded Netscape — the company that brought the internet to mainstream America. Netscape's 1995 IPO ignited the first great technology boom. Microsoft's campaign to destroy it became one of the most studied business battles in the history of capitalism.

After Netscape, he co-founded Loudcloud, which survived the dot-com collapse through one of the most dramatic corporate pivots on record — eventually reinventing itself as Opsware and selling to Hewlett-Packard for $1.65 billion.

In 2009, Andreessen and Ben Horowitz founded a16z on a contrarian thesis: that the best venture firm would be built around genuinely helping founders, not financial engineering. The firm made early bets on Facebook, Airbnb, GitHub, and Coinbase, and expanded aggressively into crypto, bio, defense, and AI.

His 2011 essay "Software Is Eating the World" reframed how an entire industry understood the stakes of the moment — and remains one of the most cited pieces of writing in the history of Silicon Valley.