The Lesser Key of Solomon or Lemegeton, erroneously called also Clavicula Salomonis (the Key of Solomon or Clavicula Salomonis is a previous book on the subject) is an anonymous grimoire, one of the most popular books on demonology.

This book appeared in the 17th century, but it seems to have been inspired by an earlier compilation from the 16th century, some mediaeval grimoires, and the real Key of Solomon. It is also possible that books written by Jewish kabbalists and Arab alchemists were also an inspiration, and perhaps (or almost surely) Pseudomonarchia Daemonum, by Johann Weyer, too.

As the book attests, it was originally written by King Solomon. The titles of nobility assigned to the demons were unknown in King Solomon's times, as well as the prayers to Jesus, and the Christian Trinity, mentioned in the book.

This book contains a detailed description of seventy-two demons (many times called spirits in the book), the conjurations needed to invoke and oblige them to do what the conjurer (called exorcist in the book) wants, the protective signs and rituals to be performed and the curses to avoid demons to gain control over the situation, the preparations the conjurer has to do before the invocations, and instructions on how to make the necessary instruments to the practice of these rituals and invocations. It also has an allusion to the thirty-one aerial spirits invoked and constraint by King Solomon.

There were several editions of this grimoire, and it is still available.

The Lesser Key of Solomon is divided in five parts: