The Advanced Disc Filing System (ADFS) is a computing file system unique to the Acorn computer range and RISC OS-based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when support for floppy discs was added (using a WD1770 floppy disc controller) and on later 32-bit systems a variant of a PC-style floppy controller.

Acorn's original Disc Filing System was limited to 31 files per disk surface, 7 characters per file name and a single character for directory names, a format inherited from the earlier Atom and System 3–5 Eurocard computers. To overcome some of these restrictions Acorn developed ADFS. The most dramatic change was the introduction of a hierarchical directory structure. The filename length increased from 7 to 10 letters and the number of files in a directory expanded to 47. It retained some superficial attributes from DFS; the directory separator continued to be a dot and $ now indicated the hierarchical root of the filesystem. ^ was used to refer to the parent directory, @ the current directory, and \ was the previously-visited directory.

The BBC Master Compact contained ADFS version 2.0, which provided the addition of format, verify and backup commands in ROM, but omitted support for hard discs.