A set-top box (STB), also colloquially known as a cable box or receiver and historically television decoder, is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of signal, turning the source signal into content in a form that can then be displayed on the television screen or other display device. They are used in cable television, satellite television, and over-the-air television systems as well as other uses.

According to the Los Angeles Times, the cost to a cable provider in the United States for a set-top box is between $150 for a basic box to $250 for a more sophisticated box. In 2016, the average pay-TV subscriber paid $231 per year to lease their set-top box from a cable service provider.