The Keep on the Borderlands is a Dungeons & Dragons adventure module by Gary Gygax, first printed in December 1979. In it, player characters are based at a keep and investigate a nearby series of caves that are filled with a variety of monsters.

It was designed to be used with the Dungeons & Dragons Basic Set, and was included in the 1979–1982 editions of the Basic Set but works fine with modern retroclones like Basic Fantasy RPG.