Vatnshyrna was a major Icelandic saga codex destroyed in the Copenhagen Fire of 1728. It was copied between 1391 and 1395 by Magnús Þórhallsson for Jón Hákonarson in northern Iceland. The codex was first called "Vatnshyrna" by Arngrímur Jónsson in his 1609 work, "Crymogaea", possibly because it was located at that time at Stóra Vatnshorn.