A phreaking box is a device used by phone phreaks to perform various functions normally reserved for operators and other telephone company employees.

Most phreaking boxes are named after colors, due to folklore surrounding the earliest boxes which suggested that the first ones of each kind were housed in a box or casing of that color. However, very few physical specimens of phreaking boxes are actually the color for which they are named.

Most phreaking boxes are electronic devices which interface directly with a telephone line and manipulate the line or the greater system in some way through either by generating audible tones that invoke switching functions (for example, a blue box), or by manipulating the electrical characteristics of the line to disrupt normal line function (for example, a black box). However a few boxes can use mechanical or acoustic methods - for example, it is possible to use a pair of properly tuned whistles as a red box.