Access control is a system which enables an authority to control access to areas and resources in a given physical facility or computer-based information system. An access control system, within the field of physical security, is generally seen as the second layer in the security of a physical structure.

Access control is, in reality, an everyday phenomenon. A lock on a car door is essentially a form of access control. A PIN on an ATM system at a bank is another means of access control. Bouncers standing in front of a night club is perhaps a more primitive mode of access control (given the evident lack of information technology involved). The possession of access control is of prime importance when persons seek to secure important, confidential, or sensitive information and equipment.

Item control or electronic key management is an area within (and possibly integrated with) an access control system which concerns the managing of possession and location of small assets or physical (mechanical) keys.