Xamarin is a San Francisco, California based software company created in May 2011 by the engineers that created Mono, Mono Touch and Mono for Android which are cross platform implementations of the Common Language Implementations (CLI) and Common Language Specifications (often called Microsoft .NET).

With a C# shared codebase, developers can use Xamarin to write native iOS, Android, and Windows apps with native user interfaces and share code across multiple platforms. Xamarin has over 505,000 developers in more than 120 countries around the world as of February 2014.

Xamarin, the popular service for building cross-platform native applications, today announced that it has raised a $54 million Series C round led by a combination of new and existing investors. As far as we are aware, that’s the largest round ever raised by a mobile app development platform.