Microsoft Windows CE (now officially known as Windows Embedded Compact and previously also known as Windows Embedded CE, and sometimes abbreviated WinCE) is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows. It is not to be confused with Windows Embedded Standard which is an NT-based componentized version of desktop Microsoft Windows.

Microsoft licenses Windows CE to OEMs and device makers. The OEMs and device makers can modify and create their own user interfaces and experiences, with Windows CE providing the technical foundation to do so.

The current version of Windows Embedded Compact supports Intel x86 and compatibles, MIPS, and ARM processors.

Windows CE is optimized for devices that have minimal storage; a Windows CE kernel may run in under a megabyte of memory. Devices are often configured without disk storage, and may be configured as a "closed" system that does not allow for end-user extension (for instance, it can be burned into ROM). Windows CE conforms to the definition of a real-time operating system, with a deterministic interrupt latency. From Version 3 and onward, the system supports 256 priority levels and uses priority inheritance for dealing with priority inversion. The fundamental unit of execution is the thread. This helps to simplify the interface and improve execution time.