Dicuil (fl late 8th century to 9th century AD) was an Irish monk and geographer. He is best known as the author of De Mensura Orbis Terram. He appears to have been based in the Frankish Kingdom in Continental Europe.
Dicuil's observations appear to include some of the earliest indications that Iceland was inhabited, and also contain possible descriptions of Shetland. He wrote about the period that the Norse were invading and settling both countries. Prior to that, there had been many Culdees in the islands, and there were some settlements of Irish monks amongst the indigenous Pictish population.<ref>http://www.libraryireland.com/SocialHistoryAncientIreland/II-VI-7.php</ref> Amongst other things Dicuil mentions:
- There are many other islands in the ocean north of Britain which can be reached from the northern islands of Britain in a direct voyage of two days and nights with sails filled in a continuously favourable wind
Not much is known about his life, but he is sometimes identified with "Hibernicus exul" (The Irish Exile)