视窗操作系统应用进程接口（Windows API），有非正式的简称法为WinAPI，是微软对于Windows操作系统中可用的核心应用进程编程接口的称法。它被设计为各种语言的进程调用，也是应用软件与Windows系统最直接的交互方式。大多数驱动进程所需要的对Windows系统的更底层次访问接口，由所用版本的Windows的Native API来提供接口。

Windows有一个软件开发包（SDK, software development kit）提供相应的文档和工具，以使进程员开发使用Windows API的软件和利用Windows技术。

The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations that are often referred to by their own names (for example, Win32 API); see the versions section. Almost all Windows programs interact with the Windows API. On the Windows NT line of operating systems, a small number (such as programs started early in the Windows startup process) use the Native API.