Webmail（基于万维网的电子邮件服务）是因特网上一种主要使用网页浏览器来阅读或发送电子邮件的服务，与使用Microsoft Outlook.com、Mozilla Thunderbird等电子邮件客户端软件的电子邮件服务相对。

因特网上的许多公司，诸如Google、雅虎、中国的新浪和网易等，都提供有webmail服务。此外，个人的因特网服务提供商也可能提供webmail，这样他们的用户可以不必通过他们一般使用的上网终端而直接使用他们的邮件服务。

Webmail (or web-based email) is any email client implemented as a web application running on a web server. Examples of webmail software are Roundcube and SquirrelMail. Examples of webmail providers are AOL Mail, Gmail, Outlook.com and Yahoo! Mail. Many webmail providers also offer email access by a desktop email client using standard email protocols, while many internet service providers provide a webmail client as part of the email service included in their internet service package. ProtonMail, founded at the CERN research facility in 2013, is a Web-based email service which automatically provides secure encryption.