Marc Lowell Andreessen ( an-DREE-sən; born July 9, 1971) is an American businessman and former software engineer. He is the co-author of Mosaic, the first widely used web browser with a graphical user interface; co-founder of Netscape; and co-founder and general partner of Silicon Valley venture capital firm Andreessen Horowitz. He co-founded and later sold the software company Opsware to Hewlett-Packard; he also co-founded Ning, a company that provides a platform for social networking websites. He is an inductee in the World Wide Web Hall of Fame. Andreessen's net worth is estimated at $1.9 billion as of January 2025.
