Unity is a cross-platform game engine developed by Unity Technologies and used to develop video games for PC, consoles, mobile devices and websites. First announced only for Mac OS, at Apple’s Worldwide Developers Conference in 2005, it has since been extended to target more than fifteen platforms. It is now the default software development kit (SDK) for the Wii U.

Unity Pro is available for a fee and Unity Personal has no fee; it is available for any use to individuals or companies with less than US$100,000 of annual gross revenue. On March 3, 2015 with the release of Unity 5.0, Unity Technologies made the complete engine available for free including all features, less source code and support. Unity is noted for an ability to target games to multiple platforms.

Five versions of Unity have been released. In 2006 at the 2006 WWDC trade show, Apple, Inc. named Unity as the runner up for its Best Use of Mac OS X Graphics category.