FreeDOS (formerly Free-DOS and PD-DOS, often abbreviated to FD or FDOS) is an operating system for IBM PC compatible computers. FreeDOS is made up of many different, separate programs that act as "packages" to the overall FreeDOS Project. As a member of the DOS family, it provides mainly disk access through its kernel, and partial memory management, but no default GUI (although OpenGEM is listed on the official FreeDOS website). FreeDOS 1.1 was released on 2 January 2012; many of the packages making up FreeDOS are updated or added to frequently.

FreeDOS supports vintage hardware IBM PCs as well as modern ones, in addition to embedded computers. Unlike MS-DOS, it is composed of free and open source software, licensed under the terms of the GNU General Public License (GPL). Its "BASE" distribution does not require license fees or royalties and creation of custom distributions is permitted. However, other sections like "UTIL" include non-GPL software considered worth preserving, such as 4DOS.