- Home: http://opensimulator.org/wiki/Main_Page
- Inspiration: Second Life
- State: beta
- Download: http://opensimulator.org/wiki/Download
- Keyword: simulation, content open
- Code repository: https://github.com/opensim/opensim.git
- Code language: C#
- Code license: 3-clause BSD
- Code dependency: MonoGame
- Assets license: ? (BSD)
Server side implementation of an open virtual 3D world in which users can create their own content. It was founded in 2007 as an open source alternative to Second Life and is compatible to Second Life clients.