Mono is an open source implementation of .NET that runs on many platforms, including Linux, Mac OS X, and Windows. This allows running .NET applications on platforms other than Windows with little to no modification.
Mono is a software platform designed to allow developers to easily create cross platform applications.
Sponsored by Xamarin, Mono is an open source implementation of Microsoft's .NET Framework based on the ECMA standards for C# and the Common Language Runtime. A growing family of solutions and an active and enthusiastic contributing community is helping position Mono to become the leading choice for development of Linux applications.