Thule is the most northerly location mentioned in ancient Greek and Roman literature and cartography. Modern interpretations have included Orkney, Shetland, Northern Scotland, the island of Saaremaa (Ösel) in Estonia, and the Norwegian island of Smøla.
In classical and medieval literature, ultima Thule (Latin “farthest Thule”) acquired a metaphorical meaning of any distant place located beyond the “borders of the known world”.
By the Late Middle Ages and the early modern period, the Greco-Roman Thule was often identified with the real Iceland or Greenland. Sometimes Ultima Thule was a Latin name for Greenland, when Thule was used for Iceland. By the late 19th century, however, Thule was frequently identified with Norway.