Yahoo! (NASDAQ: YHOO) is a U.S. public company with headquarters in Sunnyvale, California (Silicon Valley), which provides Internet services worldwide. The company is best known for its Web portal, search engine (Yahoo! Search), Yahoo! Directory, Yahoo! Mail, Yahoo! News, advertising, online mapping (Yahoo! Maps), video sharing (Dailymotion) and social media sites and services. In January 2010, Yahoo is considered the world's leading market share in online advertising. JP Morgan all of American society market share of advertising inserts is 17%, well ahead of No. 2 is 11% for Microsoft and AOL is 7%.

Yahoo! founded the Jerry Yang and David Filo in January 1994 and approved by March 1, 1995.

13th January 2009, Yahoo! appoint Carol Bartz, former CEO of Autodesk, Inc. as its new CEO and the board of directors.

According to the companies web traffic analysis (including Compete.com, comScore, Alexa Internet, Netcraft, and Nielsen notice), the domain yahoo.com attracted at least 1.575 billion visitors annually by 2008.The global network Yahoo! Sites in May to 3.4 billion impressions per day on average, than in October 2007 [Update]. It is the second most visited site in the world in May 2009.