Yesterday, Microsoft announced an agreement to acquire Xamarin, a leading platform provider for mobile app development.

In conjunction with Visual Studio, Xamarin provides a rich mobile development offering that enables developers to build mobile apps using C# and deliver fully native mobile app experiences to all major devices – including iOS, Android, and Windows.

Recently named one of the top startups that “run the Internet,” Xamarin has more than 15,000 customers in 120 countries, including more than one hundred Fortune 500 companies – and more than 1.3 million unique developers have taken advantage of their offering.

Xamarin’s unique approach to helping developers easily share common app code across their iOS, Android and Windows apps, while still delivering fully native experiences for each of the platforms, has fueled amazing growth for more than four years.

“We have had a longstanding partnership with Xamarin, and have jointly built Xamarin integration into Visual Studio, Microsoft Azure, Office 365 and the Enterprise Mobility Suite to provide developers with an end-to-end workflow for native, secure apps across platforms,” wrote Scott Guthrie, Executive Vice President of Microsoft’s Cloud and Enterprise Group. “With today’s acquisition announcement we will be taking this work much further to make our world class developer tools and services even better with deeper integration and seamless mobile app dev experiences.”

For more on the announcement, check out Scott Guthrie’s blog post. Microsoft will share more about joint plans in the near future – stream the Microsoft //Build event live or attend Xamarin Evolve to be the first to get the scoop.