A keychain or key chain is a small chain, often made from metal or plastic that connects a small item to a key ring. The length of a keychain allows an item to be used more easily than if linked directly to a keying. Some key chains allow one or both ends the aptitude to rotate, keeping the keychain from becoming twisted, while the item is being used. A keychain can also be a connecting link between a key ring and the belt of an individual. It is regularly 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 ensure that the keys remain emotionally involved to the individual using them, makes accidental loss less likely, and saves on wear and tear on the pockets of the user.

A keychain can also be a short chain used to link together a number of keys or other items. Sometimes key chains are hung on walls.