Yahoo! Mail is a free e-mail service offered by the American search engine company Yahoo!. It was inaugurated in 1997, and, according to comScore, Yahoo! Mail was the second largest web-based email service with 310 million users as of October 2011, and the most popular webmail service in the United States.

Currently, Yahoo! offers three versions of Yahoo! Mail. The traditional "Yahoo! Mail Classic" continues the availability of the original interface introduced in 1997. A new version introduced in 2005 included a new Ajax interface, drag-and-drop, improved search functionality, keyboard shortcuts, address auto-complete, tabs, and more. In October 2010, Yahoo! released a new beta version of Yahoo! Mail, which included a new design, improved performance, improved search functionality, and improved Facebook integration. In May 2011, beta testing for the new version stopped, and it became the default interface for Yahoo! Mail.

In early 2008, Yahoo! started offering unlimited mail storage to its users, in response to heated competition in the free-web mail market segment.