After more than 15 years away from undergraduate life, Sheryl K. Sandberg ’91 is now returning to the college scene.

Facebook founder Mark E. Zuckenberg, former member of the Class of 2006, has recruited Sandberg, a top Google executive, to help run the social-networking juggernaut.

Sandberg will now become Facebook’s chief operating officer.

While at Google, Sandberg led Adwords—the advertising unit that accounts for the lion’s share of Google’s annual revenue—and headed the development of Google’s philanthropic arm, Google.org.

“Sheryl was a valued member of the Google team and we wish her well in her new endeavors,” a Google spokesperson wrote in an e-mailed statement.

According to a Facebook press release, Sandberg will be in charge of sales, marketing, and business development, and will report directly to Zuckerberg, the company’s chief executive.

“Together, with Mark and the great team at Facebook, we’ll be able to scale this company into a global leader and enable Facebook users worldwide to communicate and share information better,” Sandberg said in a statement. “I am thrilled to have this opportunity.”

Prior to her six-year stint at Google, Sandberg was chief-of-staff to former University President Lawrence H. Summers when he served as secretary of the treasury from 1999 to 2001.

“Sheryl is an extraordinarily capable, organized, decisive, and caring person who will do great things for Facebook,” said Summers, who served as the advisor for Sandberg’s undergraduate honors thesis in Economics when she was at the College.

University spokesman John D. Longbrake, who knew Sandberg when he worked in communications at the Treasury, said he agreed, saying that he thought “very highly” of Sandberg.

“She was very organized and thought very strategically about the issues at the Treasury Department,” Longbrake said.

Longbrake says he thinks her experiences at Google and the Treasury will serve her well.

“The challenges the company is facing require the kinds of skills and intelligence that Sheryl Sandberg brings to the table,” he said.

Sandberg also graduated from Harvard Business School as a Baker Scholar, meaning that she was in the top five percent.

She could not be reached yesterday for an interview.

—Staff writer Clifford M. Marks contributed to the reporting of this story.