Xamarin is a Microsoft-owned, San Francisco, California-based software company. It was founded by the creators of Mono, Mono for Android, and MonoTouch, which are cross-platform implementations of the Common Language Infrastructure (CLI) and Common Language Specifications (often called Microsoft .NET).

With a C#-shared codebase, developers can use Xamarin tools to write native Android, iOS, and Windows apps. The apps have native user interfaces and share code across multiple platforms, including Windows and macOS.