GEOM is a modular I/O request transformation framework allowing kernel modules to attach to I/O devices providing a variety of layout and data transformations. GEOM was created as part of the TrustedBSD Project in order to support cryptographic disk services, such as GBDE, on the FreeBSD platform. GBDE implements strong crypographic protection of file systems at the GEOM layer.

GEOM has been present in FreeBSD since FreeBSD 5.0-RELEASE, with increasing numbers of transform modules over time, including the GELI encryption and integrity protection module.

GEOM and GBDE were implemented by Poul-Henning Kamp.