MIB may refer to:
The mebibyte is a multiple of the unit byte for digital information. The binary prefix '' mebi'' means 220; therefore 1 ''mebibyte'' is 1, 048, 576, bytes. The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission (IEC) in 1998 It was designed to replace the megabyte used in some computer science contexts to mean 220 bytes, which is similar to the SI definition of the prefix mega (106) but conflicts with it.
In '' The X-Files'' television show, the Men in Black (MIB for short, and singular, Man in Black) refer, unofficially, to a group of enforcers employed by the Syndicate to execute assassinations, cover ups and other covert operations. It is implied that most, if not all, of them are former members of special operations units. Some, mostly shown in comedic episodes, parodied the traditional view of MIBs from UFO lore. Most had no known civilian identities, though there were some exceptions. They rarely speak.