The 74-year-old resident of San Giorgio, a small town near Naples, was taken by surprise when she started pealing the potatoes and discovered an American-made hand grenade from World War II.
A bomb squad that arrived in response to her emergency call transported the grenade to the steps of Mount Vesuvius and destroyed it at a deserted site.
Police are investigating the origins of the grenade by questioning the merchant who sold the potatoes to the woman.
An important port on the Mediterranean, Naples saw heavy fighting between Allied and Axis forces during the Second World War. Units of the U.S. 82d Airborne Division took part in the capture of Naples October 1, 1943.