The appointment effective Tuesday "signals a renewed focus on product innovation to drive user experience and advertising revenue for one of the world's largest consumer Internet brands," Yahoo! said in a statement here yesterday.
The move comes as a surprise after many reports said interim CEO, Mr Ross Levinsohn, had a lock on the top job at the struggling Internet pioneer.
"I am honoured and delighted to lead Yahoo!, one of the Internet's premier destinations for more than 700 million users," Ms Mayer said in a statement.
"I look forward to working with the company's dedicated employees to bring innovative products, content and personalised experiences to users and advertisers all around the world."
At Google, Ms Mayer was responsible for local and geographical products including Google Maps, Google Earth, Zagat, Street View and local search for desktop and mobile.
She joined Google in 1999 as its 20th employee "and led efforts for many of Google's most recognisable products, including the development of its flagship search product and iconic homepage for over 10 years," the statement said.
She also "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," according to the statement.