"I know Marc will be a great mentor to me and our leadership team," Zuckerberg said of Andreessen.
"He has experience that is relevant to Facebook in so many ways: scaling companies that are experiencing extraordinary growth, creating successful technology platforms, and building strong engineering organizations."
Most recently, Andreessen has been working with Ning, a startup which aims to provide users with a platform for creating their own social networking sites. The startup is Andreessen's third, following Netscape and Opsware.
Andreessen will become the fourth member of a Facebook board that includes Zuckerberg and venture capitalists Jim Breyer and Peter Thiel.
"Facebook is one of the most innovative companies on the Web and it’s an honor to join the board," Andreessen proclaimed.
"I’m looking forward to helping the team as Facebook continues to grow."