The relic was discovered at the seventh-century Balatlar Church, in Sinop, Turkey, inside a stone chest.
"We have found a holy thing in a chest," said lead archaeologist Professor Gülgün Köroğlu."It is a piece of a cross."
"This stone chest is very important to us," said Köroğlu, who is an art historian and archeologist at Turkey's Mimar Sinan University of Fine Arts. "It has a history and is the most important artifact we have unearthed so far."
The project has unearthed more than 1,000 skeletons and the chest in question has been taken to a lab for study.
The Sinop discovery is hardly the first alleged piece of the cross on which Jesus was crucified, and many churches claim to have discovered a piece of the "true cross." According to legend, St. Helena found the cross in Jerusalem and distributed the pieces to churches in Jerusalem, Rome and Constantinople (now Istanbul).