Thirty-eight people died after the bus crashed into a guardrail and plummeted some 30 metres down a slope near the city of Avellino in Campania. The bus had been making its way back from a pilgrimage to Pietrelcina.
Simona Del Giudice, 16, from Naples, was the youngest to die, while Salvatore Testa, from Pozzuoli, was the eldest at 88.
Nearly all of those who died were from Pozzuoli, a town near Naples.
A further 19 people were injured, including a three-year-old girl, who lost her aunt and uncle in the crash, Corriere reported.
Prime Minister Enrico Letta and Laura Boldrini, the speaker of the lower house of parliament, are attending a mass funeral in Pozzuoli on Tuesday morning.
Prosecutors have launched an investigation into possible manslaughter over the accident, and will probe the company that manages the highway where the accident happened.
An autopsy has also been ordered on the driver, although police believe the crash was caused by a mechanical failure.