Revealing the news in a company blog post, Microsoft said that the update, which is free to existing Windows 8 users, will be initially available through Windows Update.
It will be available from retail stores and on new devices from October 18.
Formerly known as 'Windows Blue', Windows 8.1 promises to bring a host of improvements over its predecessor, which was initially released almost a year ago on October 26.
These include enhancements to the operating system's interface, including new ways of arranging and resizing tiles on the Start screen, and ways of snapping apps beyond the current 50:50 split snap view.
The update also sees the return of the Start button, a particular bugbear for many Windows users. Additionally, it will allow Microsoft's Surface RT and Surface Pro tablets to be used as a picture frame when in lock mode.
Surface RT users may also be looking particularly forward to being given the ability to save files directly to Microsoft's SkyDrive cloud storage service.
Other improvements to Windows 8.1 include Internet Explorer 11, which offers improved touch performance and faster page load times, according to Microsoft.
It has also modified the behavior of its hot corners and App switching so that Charm bars can be disabled to prevent them from appearing.