Beelzebub in the Bible is another name for Satan, or the Devil. He is otherwise known as Apollyon, the prince of this world, the tempter, the god of this world and the prince of the power of the air.
The name Beelzebub means "lord of the flies." The Bible refers to Satan using this name in both the Old and New Testaments. A fallen angel who rebelled against God, Satan appears in the first book of the Bible, Genesis, as a serpent tempting Eve to disobey God. Later he appears as Job's tormentor in the Book of Job, and as Jesus' tempter in the wilderness in the various gospels.