Drupal /ˈdruːpəl/ is a free and open-source content-management framework written in PHP and distributed under the GNU General Public License. It is used as a back-end framework for at least 2.1% of all Web sites worldwide ranging from personal blogs to corporate, political, and government sites. It is also used for knowledge management and business collaboration.

The standard release of Drupal, known as Drupal core, contains basic features common to content management systems. These include user account registration and maintenance, menu management, RSS feeds, taxonomy, page layout customization, and system administration. The Drupal core installation can serve as a simple Web site, a single- or multi-user blog, an Internet forum, or a community Web site providing for user-generated content.

As of April 2015, the Drupal community has provided more than 31,000 contributed modules. Such modules alter and extend the core capabilities, behavior, and appearance of a Drupal site. The Drupal community comprises more than one million members (as of October 2013) and 31,000 Developers (as of February 2014). "The Drupal Overview", a feature of the project web site, describes it as a content management framework. Drupal also describes itself as a Web application framework, as it meets the generally accepted feature requirements for such frameworks.

Although Drupal offers a sophisticated application programming interface for developers, basic Web site installation and administration of the framework require no programming skills.

Drupal runs on any computing platform that supports both a Web server capable of running PHP and a database to store content and configuration.