MySQL is a multithreaded, multi-user, SQL (Structured Query Language) Database Management System (DBMS) with an estimated six million installations. MySQL AB makes MySQL available as open source software / free software under the GNU General Public License (GPL), but they also sell it under traditional commercial licensing arrangements for cases where the intended use is incompatible with use of the GPL.

Unlike projects such as Apache, where the software is developed by a public community, and is essentially not owned by anyone, MySQL is owned and sponsored by a single for-profit firm, the Swedish company MySQL AB. The company develops and maintains the system, selling support and service contracts, as well as commercially-licensed copies of MySQL, and employing people all over the world who work together via the Internet. Two Swedes and a Finn founded MySQL AB: David Axmark, Allan Larsson, and Michael "Monty" Widenius.