In a surprise announcement, Google's Marissa Mayer was named the new CEO of Yahoo.
Yahoo said Mayer will lead "a renewed focus on product innovation to drive user experience and advertising revenue" for Yahoo.
"I am honored and delighted to lead Yahoo, one of the Internet's premier destinations for more than 700 million users," Mayer said in a statement. "I look forward to working with the company's dedicated employees to bring innovative products, content, and personalized experiences to users and advertisers all around the world."
According to the New York Times, which first reported the news, Mayer resigned from Google today via telephone and will report to Yahoo tomorrow. She will also join Yahoo's board.
"Marissa is a well-known, visionary leader in user experience and product design and one of Silicon Valley's most exciting strategists in technology development," Yahoo co-founder David Filo said in a statement. "I look forward to working with her to enhance Yahoo's product offerings for our over 700 million unique monthly visitors."
Mayer's appointment comes about two months after Scott Thompson stepped down as CEO after it was discovered that he inflated portions of his resume. Thompson, former president of eBay's PayPal unit, was hired in early January to replace Yahoo's former CEO Carol Bartz, who was unceremoniously fired several months earlier.
Mayer joined Google in 1999 as its 20th employee and first female engineer. She worked her way up to become vice president of location and local services, which made her responsible for the lifeblood of the company's search business—advertising. As PCMag pointed out recently, she's also been involved in making sure the gender balance at Google doesn't tip too male, in part by guaranteeing that there's a female engineer at each interview.
"Yahoo's products will continue to enhance our partnerships with advertisers, technology and media companies, while inspiring and delighting our users. There is a lot to do and I can't wait to get started," Mayer said.
Yahoo has faced a number of other leadership shake-ups in recent months, including the exit of co-founder Jerry Yang, chairman Roy Bostock, and three long-time board members Vyomesh Joshi, Gary Wilson, and Arthur Kern.
Earlier this week, it experienced a security breach that exposed 453,000 passwords from Yahoo Voices' users.
Yahoo is scheduled to hold its second-quarter earnings call on Tuesday afternoon.
UPDATE: In other Mayer news, the new Yahoo CEO confirmed Monday night that she is expecting her first child, a boy, in October. Mayer told Fortune that she disclosed her pregnancy to the Yahoo board before the job offer was extended and that she will take a brief maternity leave, through which she will continue to work.