Authorities at Bergamo Airport in the country's northeast discovered the egg - which measured 50 centimetres in length and 75 centimetre in diameter - in a parcel destined for Los Angeles.
The sender, who declared the egg's value to be less than €500, insisted it was a wedding gift.
The egg is thought to be from a so-called "bird elephant", or "Aepyornis Maximus", an emu-like creature weighing half a tonne.
The bird lived on the island of Madagascar during the Pleistocene era, which ended 12,000 years ago.
The sender told the Corriere Della Sera newspaper that his wife was Madagascan, and he had received the egg as a wedding gift.
"You can find eggs like this everywhere (in Madagascar) for a few euros. My wife collects them, her family has a few of them," he was quoted as saying.
The man could face a jail sentence and €5,000 fine for trying to export a cultural item without permission.