The severed head of a man said to be the patron saint of genital disease will go on auction in County Meath on Sunday.
The skull is allegedly that of St Vitalis of Assisi, an Italian Benedictine monk from the 14th century.
It belonged to an Anglo-Irish family from County Louth, and is housed in a Queen Anne case dating from the 17th century.
There has been no official verification of the claim.
St Vitalis was born in Umbria, Italy, and is said to have lived an immoral and licentious youth.
In an attempt to atone for his early sins, he later undertook pilgrimages to shrines throughout Europe, eventually entering the Benedictine monastery at Subiaco.
After leaving the monastery, he lived the remainder of his life as a hermit near Assisi.
It is said that he wore only rags and shunned all material wealth, with the exception of a basket which he used to fetch water from a nearby stream.
He died in 1370, and word of his sanctity soon spread due to reports of numerous miracles performed on those with bladder and genital disorders.
It is unclear exactly how his head may have ended up in Ireland.
Auctioneer Damien Matthews, who is selling the macabre item on Sunday, said that the family think an ancestor brought it back from the grand tour of Europe in the 18th century.
The grand tour was an educational rite of passage for wealthy Europeans from the 17th until the 19th century, intended to provide insight into the great cultural symbols of Europe.
The head sat for many years in the family hall in County Louth, but was recently uncovered in an outhouse.
Mr Matthews said that although he couldn't be certain it was the head of a saint: "It's certainly ancient, and it's certainly the head of somebody."
The Holy Cross Monastery, a Benedictine order in Rostrevor, County Down, did not even know who St Vitalis was, and after an internet search, declined to comment further on the matter of his or anyone else's severed head.
The auction takes place at Annesbrook House in Duleek, County Meath, on 29 May at 1500 BST.
The head, holy or otherwise, is valued at between 800 and 1,200 euros (between £698 and £1,047).