The ship's discovery, made during work at the site of a new road, has been hailed as an important one by archaeologists.
The wooden ship is about 11 metres long, making it one of the largest ancient vessels excavated near Ostia Antica, a port city founded 2,500 years ago that became Rome's first colony.
The ship's bow and stern are missing.
"The restoration work is very delicate as we have to continually cover the boat with water to prevent the wood drying out. It needs to be handled using very sophisticated techniques," archaeologist Anna Maria Moretti said.
The remains of the ship were found four metres below the ground during repair of a bridge linking the modern-day coastal town of Ostia to the fishing port of Fiumicino, where Rome's main airport is located.
Culture Minister Giancarlo Galan described the discovery as "spine-tingling".
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