Gubraithian Fire (or Everlasting Fire) is fire enchanted to burn forever. The enchantment seems to be an advanced-level of magic, as not many wizards are capable of doing it. Rubeus Hagrid and Madame Maxime gave this to the Gurg of the Giants as a gift and proof of good faith.
The name "Gubraithian" is evidently taken from the Scottish Gaelic phrase "gu brath", which means "forever".
- Harry Potter and the Order of the Phoenix (Mentioned only)