File Allocation Table (FAT) is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras.

FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of its relative simplicity. Performance of FAT compares poorly to most other file systems as it uses overly simplistic data structures, making file operations time-consuming, and makes poor use of disk space in situations where many small files are present.

For floppy disks, the FAT has been standardized as ECMA-107[1] and ISO/IEC 9293.[2][3] Those standards include only FAT12 and FAT16 without long filename support; long filenames with FAT is partially patented.

The FAT file system is relatively straightforward technically and is supported by virtually all existing operating systems for personal computers. This makes it a useful format for solid-state memory cards and a convenient way to share data between operating systems.