The MIT License is a free software license originating at the Massachusetts Institute of Technology (MIT). It is a permissive license, meaning that it permits reuse within proprietary software on the condition that the license is distributed with that software, and GPL-compatible, meaning that the GPL permits combination and redistribution with software that uses the MIT License.

According to the Free Software Foundation, the MIT License is more accurately called the X11 license, since MIT has used many licenses for software and the license was first drafted for the X Window System.

Software packages that use the MIT License include Expat, PuTTY, Mono development platform class libraries, Ruby on Rails, Twisted, Lua 5.0 onwards and the X Window System, for which the license was written.

Some software packages dual license their products under the MIT License, such as older versions of the cURL library, which allowed recipients to choose either the Mozilla Public License or the MIT License.