An elven-forged longsword, discovered in a stone troll hoard by Bilbo Baggins and company, as told in The Hobbit (or more correctly, There and Back Again). Like Glamdring and Sting, the blade glows blue in the presence of the servants of Sauron.
After its discovery, it was carried by the dwarf Thorin Oakenshield during the quest to free Erebor from the evil dragon Smaug. It is not clear what happens to Orcrist following Thorin's death.