The animal was found hidden under the clay floor of a storehouse and probably died before Vesuvius erupted.
"It had dug itself a burrow where it could lay its egg, but failed to do, which may have caused its death," said Valeria Amoretti, who works as an anthropologist at the site.
The unusual find came to light during excavations of an area that had been devastated by a violent earthquake in 62 AD and was subsequently absorbed into a public bath house.
The site was originally an opulent home with refined mosaics and wall paintings, dating back to the 1st century BC, and archaeologists are not sure why the building was not restored but was rather taken over by the Stabian baths.
"Both the presence of the tortoise in the city and the abandonment of the sumptuous domus... illustrate the extent of the transformations after the earthquake in 62 AD," said Gabriel Zuchtriegel, director general of Pompeii.
"Evidently not all the houses were rebuilt and areas, even central ones, of the city were scarcely frequented to the extent that they became the habitat of wild animals."
"At the same time, the expansion of the baths is evidence of the great confidence with which Pompeii restarted after the earthquake, only to be crushed in a single day in AD 79."