A hidden camera or spy camera is a camera used to photograph or record subjects, often people, without their knowledge. The camera may be considered "hidden" because it is not visible to the subject being filmed, or is disguised as another object. Hidden cameras are often considered a surveillance tool.

Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing or directing. This can include observation from a distance by means of electronic equipment, such as closed-circuit television (CCTV), or interception of electronically transmitted information like Internet traffic. It can also include simple technical methods, such as human intelligence gathering and postal interception.