In a move that surprised everybody, long-time Google Inc (NASDAQ:GOOG) executive Marissa Mayer has been appointed as the president and CEO of Yahoo! Inc. (NASDAQ:YHOO). Ms. Mayer, who was the first female engineer at Google, is known for playing key role in bringing some of the Google’s most popular products such as Gmail, Google Maps, Google Images and Google News.

Her appointment is considered to be a good sign for Yahoo! Inc. (NASDAQ:YHOO), which has struggled for a long time to attract top level talents. As the new CEO of Yahoo, Mayer is one of the very few women in the top spot in Silicon Valley. Analysts were expecting the job would go to interim CEO Ross Levinsohn, who has been running Yahoo since former CEO Scot Thompson left the company.

For the past few months, Mayer had been seeking opportunities outside of Google Inc (NASDAQ:GOOG) to pursue grander ambitions. She joined the board of Wal-mart on April. The New York Times says that Ms. Mayer resigned from Google on Monday, and will officially join Yahoo on Tuesday. She is also likely to join the board of Yahoo.

Mayer said she was first approached by Yahoo in June. Talking about reviving Yahoo, she says she would like to leverage the company’s strong franchises such as e-mail, finance and sports.

Clearly, Yahoo made the decision to provide the news of the change directly to the Times; as of right this minute the company has neither issued a press release nor filed with the SEC to officially disclose the change. In fact, the headline on Yahoo Finance about the CEO change links to the Times story, and not to any official announcement from the company.

Yahoo just announced officially in a press release about the appointment of Marissa Mayer as the new CEO. Here is the official announcement:

Yahoo! (YAHOO) today announced that it has appointed Marissa Mayer as President and Chief Executive Officer and Member of the Board of Directors effective July 17, 2012. The appointment of Ms. Mayer, a leading consumer Internet executive, signals a renewed focus on product innovation to drive user experience and advertising revenue for one of the world’s largest consumer Internet brands, whose leading properties include Yahoo! Finance, Yahoo! Sports, Yahoo! Mobile, Yahoo! Mail, and Yahoo! Search.

Mayer said, “I am honored and delighted to lead Yahoo!, one of the Internet’s premier destinations for more than 700 million users. 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.”

Most recently, Mayer was responsible for Local, Maps, and Location Services for Google, the company’s suite of local and geographical products including Google Maps, Google Earth, Zagat, Street View, and Local Search, for desktop and mobile. Mayer joined Google in 1999 as its 20th employee and led efforts for many of Google’s most recognizable products, including the development of its flagship search product and iconic homepage for over 10 years. Mayer managed some of Google’s most successful innovations, launching more than 100 features and products including image, book and product Search, Toolbar, iGoogle, Google News, and Gmail – creating much of the “look and feel” of the Google user experience.

Yahoo! Co-Founder David Filo said, “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. I look forward to working with her to enhance Yahoo’s product offerings for our over 700 million unique monthly visitors.”

“The Board of Directors unanimously agreed that Marissa’s unparalleled track record in technology, design, and product execution makes her the right leader for Yahoo! at this time of enormous opportunity,” said Fred Amoroso, Chairman of the Board of Directors.

Mayer received her B.S. in Symbolic Systems and her M.S. in Computer Science from Stanford University, specializing in artificial intelligence for both degrees. She is credited as an inventor on several patents in artificial intelligence and interface design.

“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.