Flateyjarbók is the name given to GKS 1005 fol., a manuscript now housed at the Árni Magnússon Institute (Stofnun Árna Magnússonar á Íslandi) in Reykjavík, Iceland. It is the largest of the extant medieval Icelandic manuscripts and is beautifully illuminated with historical initials. In its original form it contained 202 leaves, with the text laid out in two columns to the page. It is so well preserved that not a single leaf is missing and each word is still legible. The manuscript was commissioned by Jón Hákonarson (b. 1350, d. 1416), a wealthy farmer living at Víðidalstunga in the northern Iceland, and it was written in the area, most likely at Víðidalstunga or at the nearby monastery of þingeyrar.