The severed head, which is housed in an ornate case, will be offered for sale in Duleek, Ireland by Matthews Auction Rooms.
It had been kept in the entrance hall of the owner's home, but when children arrived it was stored in an old outhouse.
"That's where I came across it," auctioneer Damien Matthews told the Belfast Telegraph
. "It is strange and it is macabre but it is very interesting object."
The Meath Chronicle
reported that Saint Vitalis of Assisi, who died in 1370, is thought to have been an Italian hermit and monk. He was immoral as a youth, and later tried to make up for his sins by taking part in pilgrimages and living in poverty. He became known as a patron against genital diseases.
The family selling the head believe someone may have bought it during a grand tour of Europe in the 18th century, and then brought it to Ireland.
While no one knows for sure if the head is that of St Vitalis of Assisi, it is valued at between €800 and €1,200 (£698-£1,047 - $1,138-$1,707).
"It's certainly ancient, and it's certainly the head of somebody," the BBC
quoted Matthews as saying.
A large photo of the item can be seen on the Toronto Sun