Windows Millennium Edition, or Windows ME (marketed as being pronounced as the pronoun "Me" , but commonly pronounced as an initialism, "M-E"), is a graphical operating system from Microsoft released to manufacturing on June 19, 2000 and launched on September 14, 2000.It was the last operating system released in the Windows 9x series.

Windows ME was the successor to Windows 98 SE and was targeted specifically at home PC users. It included Internet Explorer 5.5, Windows Media Player 7, and the new Windows Movie Maker software, which provided basic video editing and was designed to be easy to use for home users. Microsoft also updated the graphical user interface, shell features, and Windows Explorer in Windows ME with some of those first introduced in Windows 2000, which had been released as a business-oriented operating system seven months earlier. Windows ME could be upgraded to Internet Explorer 6 SP1 (but not to SP2 (SV1) or Internet Explorer 7), Outlook Express 6 SP1 and Windows Media Player 9 Series. Microsoft .NET Framework up to and including version 2.0 is supported; however, versions 2.0 SP1, 3.x, and greater are not. Office XP was the last version of Microsoft Office to be compatible with Windows ME.

Windows ME is a continuation of the Windows 9x model, but with restricted access to real mode MS-DOS in order to decrease system boot time. This was one of the most unpopular changes in Windows ME, because applications that needed real mode DOS to run, such as older disk utilities, did not run under Windows ME (although the system could either be booted into real mode DOS using a bootable Windows ME floppy disk or the configuration could be tweaked manually to reenable access to the underlying MS-DOS).

Compared with other releases of Windows, Windows ME had a short shelf-life of just over a year. Microsoft aimed to make ME the first consumer Windows OS based on the NT kernel. However, this did not happen and ME was rushed to the market after the Neptune project was canceled. Windows ME was often criticized for being buggy, slow and unstable. Windows ME, along with Windows 2000, were soon replaced by the NT-based Windows XP, which was launched on August 24, 2001. Support for Windows ME ended on July 11, 2006.