The Microdrive is a brand name for a miniature, 1-inch hard disk designed to fit in a Compact Flash (CF) Type II slot. The release of similar drives by other makers has led to them often being referred to as 'microdrives'. However, 'microdrive' is not a genericized trademark and manufacturers other than IBM up to 2003 and Hitachi after do not officially refer to these drives as Microdrives. Some other companies, such as Sony, have licensed the name and sell re-branded versions.

These drives fit into any CompactFlash II slot; however, they may consume more power than flash memory (currents on the order of 190 mA, peak 310 mA, at 3.3 V) and therefore may not work in some low-power devices (e.g. handheld computers). Nevertheless, they have some benefits over flash memory in terms of the way data is stored and manipulated. Microdrives can store 4 GB or more, but must be formatted for a file system which supports this capacity, such as FAT 32 or NTFS, which may not be supported by older CompactFlash hosts, but it is possible to partition a drive so it will contain a partition less than 4 GB.