Janus Galloglass was a shop located in Diagon Alley in London, England. It sold a variety of magical mirrors, including scrying mirrors, enchanted mirrors, and haunted mirrors. It had a top floor in the attic for Blinkhorn's workshop. It also had a psychomanteum available for its patrons to use. It was located near Noltie's Botanical Novelties and Praedico Predico. 
- Janus, in ancient Roman religion and myth, is the god of beginnings and transitions. He is usually depicted with two opposing faces, which would suggest something mirrored.
- "Galloglass" appears to be a portmanteau of Galleon, a wizarding form of currency, and "glass".
- The name Galloglass is an English translation of the Irish Galloglaigh (gall oglaigh), meaning "foreign young warriors" - which is what the Irish called the Scottish-Norse tribes .
- Harry Potter and the Philosopher's Stone (First appearance) (Deluxe Illustrated Slipcase Edition)