Magnum may refer to:

• Any cartridge possessing enhanced or more desirable ballistic characteristics when compared to others using the same parent case (.357 Magnum vs. .38 Special) by way of extended casing, bullet shape, body width, taper etc. The cartridge must differ from the parent in some way: if it is dimensionally identical then is not a Magnum cartridge, it is instead an overpressure cartridge (+P or +P+).

• Any weapon designed to fire such cartridges