Mithril is a fictional metal found in J. R. R. Tolkien's Middle-earth writings. It is described as resembling silver, but being stronger and lighter than steel. It was used to make armour, such as the helmets of the citadel guard of Minas Tirith, and ithildin alloy, used to decorate gateways with writing visible only by starlight or moonlight. Always extremely valuable, by the end of the Third Age it was beyond price, and only a few arte<!--British English-->facts made of it remained in use.
Impenetrable armour occurs in Norse mythology in Hervarar saga ok Heiðreks, a story that Tolkien certainly knew and could have used for his mithril mail-coat. Mithril is the only invented metal in his Middle-earth writings. Chemists<!-- A little later the narrator describes "a small coat of mail, wrought for some young elf-prince long ago. It was of silver-steel which the elves call mithril".
The Noldor of Eregion, the Elvish land to the west of Moria, made an alloy from it called ithildin ("star moon"), used to decorate gateways, portals and pathways. It was visible only by starlight or moonlight. The West Gate of Moria bore inlaid ithildin designs and runes. and the inaccessible continent of Aman. In the first 1937 edition, the mail shirt given to Bilbo Baggins is described as being made of "silvered steel".