• mscorlib.dll
• System.dll
• System.Xml.dll
• System.Runtime.Remoting.dll
• System.Data.dll
• System.Drawing.dll
• System.Web.dll
• System.Web.Services.dll
• System.Windows.Forms.dll

Some of the namespaces, modules and types in the F# library are:

• (Click here for the full index of namespaces and types).
• Microsoft.FSharp.Core - Basic type definitions and abbreviations, including definitions for options, tuple and function types. This namespace is automatically opened for every source code file.
• Microsoft.FSharp.Collections - Object-oriented views of some F# collection types.
• Microsoft.FSharp.Math.Types.BigNum - The type of arbitrary-precision rationals. Operations over this type are defined in the related module of operations Microsoft.FSharp.Math.BigNum.
• Microsoft.FSharp.Math.Types.BigInt - The type of arbitrary-precision integers. Operations over this type are defined in the related module of operations Microsoft.FSharp.Math.BigInt.
• Microsoft.FSharp.Math.Types.Matrix - The type of generic matrices. Operations over this type are defined in the related module of operations Microsoft.FSharp.Math.Matrix.
• Microsoft.FSharp.Reflection - Types and operations that augment the .NET reflection library with the ability to access F# types and values via a generic representation.
• Microsoft.FSharp.Quotations - Library support for lifted term quotation.
• Microsoft.FSharp.Compatibility - .NET-compatible array constructs, only for use when your F# code to target version 1.0 or 1.1 of the CLR.

This namespaces Microsoft.FSharp.Core, Microsoft.FSharp.Collections, Microsoft.FSharp.Control and Microsoft.FSharp.Text are automatically opened for every source code file, as is the module Microsoft.FSharp.Core.Operators. This means modules such as Microsoft.FSharp.Collections.List can typically be opened just by using open List.

Some modules are primarily of interest for those cross-compiling OCaml code, e.g. those under the Microsoft.FSharp.Compatibility.OCaml namespace.