DOS 4 or DOS-4 may refer to:
The Soviet space station Salyut 4
Versions of the IBM PC DOS family: IBM DOS 3.40, announced successor of IBM DOS 3.30 in 1988 IBM DOS 4.00, released successor of IBM DOS 3.40 in 1988 IBM DOS 4.01, a bug-fix release at the end of the same year IBM DOS 4.02, a ROMed version of DOS in IBM PS/1 machines
Versions of the Microsoft MS-DOS family: MS-DOS 4.0 (multitasking), a multitasking version in 1986/1987 by Microsoft MS-DOS 4.1 (multitasking), a multitasking version for the ICL DRS PWS in 1987 MS-DOS 3.40, announced successor of MS-DOS 3.31 in 1988 MS-DOS 4.00 (IBM-developed), successor to MS-DOS 3.31 in 1988 MS-DOS 4.01, a bug-fix release in 1988 Russian MS-DOS 4.01, a special Russian version of MS-DOS 4.01 (RDOS) in 1990
See also 4DOS DOS (disambiguation) DOS 3 (disambiguation) DOS 5 (disambiguation)