Experts said the relic, which dates to about 750 A.D., is in exceptionally good condition.
"It's quite unusual to find remnants from the Viking age that are so well-preserved ... it might be used today if you sharpened the edge," conservator Per Morten Ekerhovd told CNN.
The weapon, which was covered in rust, was found lying under rocks on a path about 150 miles west of Oslo.
It was found without a handle and is made of wrought iron. Some believe that it could be from a traveler or a burial site, CNN reported.