This chapter introduces Joomla, an open source content management system (CMS) used to build websites. Joomla is derived from the Swahili word meaning "all together" and is the result of a discussion between the Mambo Foundation and its development team in 2005. Joomla has seen major version releases over the years including 1.0, 1.5, 1.6, 1.7, and the upcoming long term support (LTS) version 2.5. Joomla is used worldwide on simple homepages and complex corporate websites due to its ease of installation, management, and reliability. While many existing users have upgraded over the years, there are still those unfamiliar with the system.