David Taylor of County Down said he found the object while lifting stones in a field near Kircubbin and his wife told him it was an old bull ring and he should throw it out, the BBC reported Monday.
"I just knew by the shape of it, it was something," Taylor said.
Taylor said experts identified the object as a silver Viking ring from between the 10th and 12th centuries.
University College Cork archaeologist John Sheehan said the ring was found near the ruins of a medieval church and may have been stolen from Viking settlers.
"Maybe it fell into Irish hands and as a result of that ended up deposited for safe-keeping at a church site but then got lost," he said.
The ring is being sent to the U.K's Treasure Valuation Committee for appraisal.