Facebook Inc. said Chief Operating Officer Sheryl Sandberg will become a director, adding the first woman to a seven-man board.

“Sheryl has been my partner in running Facebook and has been central to our growth and success over the years,” Chief Executive Officer Mark Zuckerberg 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.’’

Facebook has been seeking to add directors, including at least one woman, who can add diversity to its all-male board, people with knowledge of the matter said last month. The world’s largest social-networking service has drawn scrutiny for the lack of independent directors and gender diversity on its board, even as most of its 901 million users are women.