Baal is a Judeo-Christian demon. His name also refers to various gods and goddesses who are not demons. This is a potential source of confusion. In this article, the name Baal is used only to refer to the demon Baal, unless stated otherwise.

Until archaeological digs at Ras Shamra and Ebla uncovered texts explaining the Syrian pantheon, the demon Ba‘al Zebûb was frequently confused with various Semitic spirits and deities entitled Ba‘al, and in some Christian writings it might refer to a high-ranking devil or to Satan himself.

In the ancient world of the Persian Empire, from the Persian Gulf to the Mediterranean Sea, worship of wooden and metal idols was being rejected in favor of the Abrahamic god.[citation needed] In the Levant the idols were called "ba`als", each of which represented a local spirit-deity or "demon". Worship of all such spirits was rejected as wrong and many were in fact considered malevolent and dangerous.

Originally, the Semitic god Hadad was worshipped by Arameans who brought his worship to other parts of the Mediterranean. He is also called "The Lord" (Ba`al) and ruled over the high gods assembled on the holy mount of Heaven.

Early demonologists, unaware of Hadad or that "Ba`al" in the Bible referred to any number of local spirits, came to regard the term as referring to but one personage. The idea of Baal as one specific demon was prevalent in early Christianity. Early Christianity regarded ancient gods as demons (mere spirits, whether good or evil) and demonology divided the demonic population of Hell in several hierarchies.

In this unholy hierarchy, Baal (usually spelt "Bael" in this context; there is a possibility that the two figures aren't connected) was ranked as the first and principal king in Hell, ruling over the East. According to some authors, Baal is a Duke, with sixty-six legions of demons under his command.

During the English Puritan period, Baal was either compared to Satan or considered his main assistant. According to Francis Barrett, he has the power to make those who invoke him invisible, and to some other demonologists his power is stronger in October. According to some sources, he can make people wise, and speaks hoarsely.

While his Semitic predecessor was depicted as a man or a bull, the demon Baal was in grimoire tradition said to appear in the forms of a man, cat, toad, or combinations thereof. An illustration in Collin de Plancy's 1818 book Dictionnaire Infernal rather curiously placed the heads of the three creatures onto a set of spider legs.