Facebook Inc named Chief Operating Officer Sheryl Sandberg a director on Monday, adding the first woman to a board that includes seven men.

For years one of the most vocal critics of the gender imbalance in Silicon Valley's executive ranks, Sandberg, 42, joined Facebook in 2008 and played a central role in guiding the social networking company to its $16 billion IPO in May.

Her promotion comes as Facebook seeks to cultivate a more mature image, as opposed to the college dorm-room startup reputation that has lingered conspicuously since Harvard dropout Mark Zuckerberg founded the company in 2004.

"Sheryl has been my partner in running Facebook and has been central to our growth and success over the years," Zuckerberg, 28, said in a statement. "Her understanding of our mission and long-term opportunity, and her experience both at Facebook and on public company boards makes her a natural fit for our board."

Prior to joining Facebook, Sandberg worked at Google , where she was credited for building the search advertising division into a massively lucrative cornerstone of the web giant's business.

She has been tasked with stoking similar revenue growth at Facebook, which made $3.7 billion last year.

At the same time, Facebook hopes the promotion of one of corporate America's most high-profile women will go some way to soothe concerns over its own gender issues, especially given Sandberg's advocacy on the subject.

Before Facebook went public February, the California State Teachers' Retirement System, the second-largest largest pension fund in the United States, openly urged on the company to diversify its board to include women, calling the makeup of the all-male panel at the time "disappointing."

Facebook faced embarrassment as recently as last week, when the Wall Street Journal published advance excerpts of a memoir by Katherine Losse, an early employee who recounted being harassed and propositioned by male co-workers until Sandberg intervened when she joined the company.

In recent years, Sandberg's clout within Facebook has been unquestioned while she has served as a public deputy to the sometimes socially-awkward Zuckerberg, appearing regularly at events like the World Economic Forum in Davos, Switzerland - where she led a panel on women's advancement in January.

Sandberg, a former chief of staff to Treasury Secretary Lawrence Summers during the Clinton administration, also serves on the board of Walt Disney Co and several non-profit organizations.

Aside from Sandberg, Facebook's board comprises of seven men, including Zuckerberg; venture capitalists James W. Breyer, Marc Andreessen and Peter Thiel; The Washington Post Co Chairman Donald E. Graham; Netflix CEO Reed Hastings and Erskine Bowles, the University of North Carolina president.