Hi-MD is a magneto-optical disc-based data storage format. It was a further development of the MiniDisc. With its release in later 2004, came the ability to use newly developed, high-capacity 1 gigabyte Hi-MD discs, in the same dimensions as MiniDisc. The last recorder and player was discontinued in 2011. Blank discs stopped production in September 2012.

A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. 130 mm (5.25 in) and 90 mm (3.5 in) discs were the most common sizes. In 1983, just a year after the introduction of the compact disc, Kees Schouhamer Immink and Joseph Braat presented the first experiments with erasable magneto-optical compact discs during the 73rd AES Convention in Eindhoven. The technology was introduced commercially in 1985. Although optical, they normally appear as hard disk drives to an operating system and can be formatted with any file system. Magneto-optical drives were common in some countries, such as Japan, but have fallen into disuse.