A keychain (also key fob or keyring) is a small ring or chain of metal to which several keys can be attached. The length of a keychain allows an item to be used more easily than if connected directly to a keyring. Some keychains allow one or both ends to rotate, keeping the keychain from becoming twisted, while the item is being used.

A keychain can also be a connecting link between a keyring and the belt of an individual. It is usually employed by personnel whose job demands frequent use of keys, such as a security guard, prison officer, janitor, or retail store manager. The chain is often retractable, and therefore may be a nylon rope, instead of an actual metal chain. The chain ensures that the keys remain attached to the individual using them, makes accidental loss less likely, and saves on wear and tear on the pockets of the user.