In a general sense, a lock-out chip is a chip within an electronic device to prevent other manufacturers from using a company's device to perform certain functions.

The most famous example is the lock-out chip found in Nintendo's Famicom (NES), known also as the Neg-5 Chip, designed to prevent "unlicensed" manufacturers from creating games for the console. The presence of the chip forced unlicensed companies to raise the price of each cartridge (due to the fact a bypass chip had to be added to the cartridge), and allowed Nintendo a tiny foothold for a dubious lawsuit. Though Nintendo never really had a case against these manufacturers, taking them to court was usually enough to render the offending company bankrupt. The one exception is Color Dreams whose religious-themed games under the subsidiary Wisdom Tree made Nintendo wary of creating a public backlash for "persecution".