What is the equivalent JVM in C#?

The Common Language Runtime or CLR. This is the runtime that supports not just C# but also other .NET languages, such as Visual Basic.NET. Typically, each language exposes developers to a subset of the features available on the CLR (for instance, method overloading purely by return type is not generally supported in C#, but is supported by the CLR).

Just as Java compiles to bytecode, C# and other .NET languages compile to Microsoft Intermediate Language (MSIL) - the only language to expose the complete set of CLR features.

Of course, C# is defined purely as a language. There's no reason why it cannot be made to run on other runtimes, or indeed in an interpreted mode. But the "equivalent" of "the" JVM (implying the default one) is the CLR.

You need to have Common Language Runtime (CLR ) to run C# applications.