A magnet (from Greek magnḗtis líthos, "Magnesian stone") is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.

The Magnet URI scheme, defines the format of magnet links, a de facto standard for identifying files by their content, via cryptographic hash value rather than by their location.