Count Alessandro di Cagliostro was the alias of the occultist Giuseppe Balsamo, an Italian adventurer and self-styled magician. He became a glamorous figure associated with the royal courts of Europe where he pursued various occult arts, including psychic healing, alchemy and scrying. His reputation lingered for many decades after his death, but continued to deteriorate, as he came to be regarded as a charlatan and impostor.
- Mrs. Zimmermann uses spells favored by Count Cagliostro, and others, in her attempt to get the magic eight ball to respond (The House with a Clock in its Walls, 164).
- Professor Childermass asks if Johnny and Fergie are familiar with "charlatans" such as Comte de Saint-Germain and Cagliostro (The Bell, the Book, and the Spellbinder, 22).
- Jarmyn Cudbright appears as an associate of Count Alessandro di Cagliostro (Bell, 100).
- In 1778, Cagliostro, Saint-Germain, and Jarmyn Cudbright discuss the ability to live 5,557 years (Bell, 101).