As a top executive at Google for the past 13 years, Marissa Mayer played an instrumental role in developing many of the services that have tormented Yahoo as its appeal waned among Web surfers, advertisers and investors.
Now, Yahoo is turning to its longtime nemesis to fix everything that has gone wrong while Google has been cementing its position as the Internet's most powerful company.
Mayer, 37, took over Tuesday as Yahoo's fifth CEO in the past five years.
"I just saw a huge opportunity to have a global impact on users and really help the company in terms of managing its portfolio, attracting great talent and really inspiring and delighting people," Mayer said late Monday.
Within a few months, Mayer expects to be on a maternity leave. Mayer revealed Monday to Fortune magazine that she is pregnant with a boy. Her due date is Oct. 7. She said she had informed Yahoo's board about her pregnancy before the 11 directors unanimously voted to hire her.
Like her predecessors, Mayer will have to come up with an effective strategy to compete with the juggernaut Google has become and the increasingly influential force that Facebook is turning into as more people immerse themselves in its social network.
Yahoo's stock has been slumping since it balked at a chance to sell itself to Microsoft for $47.5 billion, or $33 per share, in May 2008. Yahoo shares haven't traded above $20 since September 2008.
Although her responsibilities at Google were narrowed two years ago, Mayer is still widely considered to be among the Internet industry's brightest executives. A Wisconsin native, Mayer is a mathematics whiz with a spongelike memory and a keen eye for design.
Mayer joined Google in 1999 as its 20th employee and went on to play an integral role in helping co-founders Larry Page and Sergey Brin exploit their online search technology to outmaneuver Yahoo at a time when it was still the larger of the two companies. Now, it takes Google a little more than a month to generate as much revenue as Yahoo does in a year.
During Google's rise, Mayer helped oversee the development and design of the company's popular email, online mapping and news services. She also became a topic of Silicon Valley gossip during Google's early years while she dated Page for three years. They have since married other people.
"We will miss her talents," Page, now the company's CEO, said in a statement.
Yahoo picked Mayer over an internal candidate, Ross Levinsohn, who had been widely considered to be the front-runner for the job after stepping in to fill a void created two months ago when the company dumped Scott Thompson as CEO amid a flap over misinformation on his official biography.