A grimoire (/ɡrɪmˈwɑːr/) (also known as a book of spells, magic book, or a spellbook) is a textbook of magic, typically including instructions on how to create magical objects like talismans and amulets; how to perform magical spells, charms, and divination; and how to summon or invoke supernatural entities such as angels, spirits, deities, and demons. In many cases, the books themselves are believed to be imbued with magical powers. The only contents found in a grimoire are information on spells, rituals, the preparation of magical tools, and lists of ingredients and their magical correspondences.^{[unreliable source?]} In this manner, while all books on magic could be thought of as grimoires, not all magical books should be thought of as grimoires.

While the term grimoire is originally European—and many Europeans throughout history, particularly ceremonial magicians and cunning folk, have used grimoires—the historian Owen Davies has noted that similar books can be found all around the world, ranging from Jamaica to Sumatra. He also noted that in this sense, the world's first grimoires were created in Europe and the ancient Near East.

The etymology of grimoire is unclear. It is most commonly believed that the term grimoire originated from the Old French word grammaire 'grammar', which had initially been used to refer to all books written in Latin. By the 18th century, the term had gained its now common usage in France and had begun to be used to refer purely to books of magic. Owen Davies presumed this was because "many of them continued to circulate in Latin manuscripts".

However, the term grimoire later developed into a figure of speech among the French indicating something that was hard to understand. In the 19th century, with the increasing interest in occultism among the British following the publication of Francis Barrett's The Magus (1801), the term entered English in reference to books of magic.

The earliest known written magical incantations come from ancient Mesopotamia (modern Iraq), where they have been found inscribed on cuneiform clay tablets that archaeologists excavated from the city of Uruk and dated to between the 5th and 4th centuries BC. The ancient Egyptians also employed magical incantations, which have been found inscribed on amulets and other items. The Egyptian magical system, known as heka, was greatly altered and expanded after the Macedonians, led by Alexander the Great, invaded Egypt in 332 BC.

Under the next three centuries of Hellenistic Egypt, the Coptic writing system evolved, and the Library of Alexandria was opened. This likely had an influence upon books of magic, with the trend on known incantations switching from simple health and protection charms to more specific things, such as financial success and sexual fulfillment. Around this time the legendary figure of Hermes Trismegistus developed as a conflation of the Egyptian god Thoth and the Greek Hermes; this figure was associated with writing and magic and, therefore, of books on magic.

The ancient Greeks and Romans believed that books on magic were invented by the Persians. The 1st-century AD writer Pliny the Elder stated that magic had been first discovered by the ancient philosopher Zoroaster around the year 647 BC but that it was only written down in the 5th century BC by the magician Osthanes. His claims are not, however, supported by modern historians.

The ancient Jewish people were often viewed as being knowledgeable in magic, which, according to legend, they had learned from Moses, who had learned it in Egypt. Among many ancient writers, Moses was seen as an Egyptian rather than a Jew. Two manuscripts likely dating to the 4th century, both of which purport to be the legendary eighth Book of Moses (the first five being the initial books in the Biblical Old Testament), present him as a polytheist who explained how to conjure gods and subdue demons.