The Mozilla Public License (MPL) is a free and open-source software license developed and maintained by the Mozilla Foundation. It is a weak copyleft license, characterized as a middle ground between permissive software licenses and the GNU General Public License (GPL), that seeks to balance the concerns of proprietary and open-source developers. As such, it allows the integration of MPL-licensed code into proprietary codebases, as long as the MPL-licensed components remain accessible under the terms of the MPL.

It has undergone two revisions: a minor update to version 1.1, and a major update to version 2.0 with the goals of greater simplicity and better compatibility with other licenses.

The MPL is the license for Mozilla Firefox, Mozilla Thunderbird, and most other Mozilla software, but it has been used by others, such as Adobe to license their Flex product line, and The Document Foundation to license LibreOffice 4.0 (also on LGPL 3+). Version 1.1 was adapted by several projects to form derivative licenses like Sun Microsystems' own Common Development and Distribution License.