MinWin is a term used informally by Microsoft to describe the kernel and operating system components that form the basis of releases of Microsoft Windows starting with Windows Vista. The term was first used in 2003 to describe approximately 95% of the common components of the operating system, but has over time come to refer to a significantly smaller portion.

Microsoft has also used the term OneCore to describe the set of Windows components that comprised MinWin.

Through the history of Microsoft Windows, the core of the operating system was generally designed to be a single large, inter-related set of components. With successive releases, the set of components considered to be the core of Microsoft Windows numbered into the thousands, with numerous dependencies that prevented the company from producing a version of Microsoft Windows that (for example) didn't include the graphical user interface and printing components. Further complicating this was the issue that many configuration tasks could only be performed using the graphical user interface.

In an April 2003 interview coinciding with the release of Windows Server 2003, Rob Short, the vice-president of the Windows Core Technology group, explained that creating a command-line version would involve "looking at the layers and what's available at each layer and how do we make it much closer to the thing the Linux guys have -- having only the pieces you want running. That's something Linux has that's ahead of us, but we're looking at it. We will have a command line-only version, but whether it'll have all the features in is another matter. A lot of the tools depend on having the graphical interface." Windows Server 2003 was seen by reviewers such as Direction On Microsoft's Michael Cherry as having reduced the reliance on graphical tools to configure the operating system, but the operating system itself still required the full graphical interface to be installed, even on servers where it would never be needed.

After Windows Server 2003's release, Rob Short assembled a team of kernel architects at Microsoft, with the intention of untangling and documenting the dependencies within the core operating system. The kernel development team had realized that they were having difficulty being able to "predict the impact of changes and to make broad, cross-group changes to Windows", and the new kernel architecture team would aim to improve software engineering practices both within the Windows kernel itself, as well as with the other components of Windows. To do this, every component of the operating system (consisting of about 5,500 distinct files in late 2005, during the development of Windows Vista) was assigned a "layer number" that represents its dependency position relative to other components, with lower-numbered components being closer to the core of the operating system, and higher numbers representing high-level components. With this information, the core architecture team began to address a range of issues where low-level components were reliant on high-level components, and finding ways to resolve those dependencies. In doing so, a number of new options for creating focused sub-sets of Windows for different purposes became possible.

This effort culminated with Microsoft shipping MinWin based Windows 10 Anniversary Update (1607) in 2016 which powered PCs, Servers, Xbox Consoles, Microsoft's HoloLens devices, and Microsoft's SurfaceHub devices.

In 2023, Microsoft announced that its Azure fleet of servers runs a MinWin (a.k.a. OneCore) based version of Windows, tailor made for Azure, called Azure Host OS.

While Microsoft has stated that MinWin will not be released as a stand-alone product, the various iterations of MinWin have shipped in every Windows operating system release since Windows Vista.