The Basilica of San Petronio is the main church of Bologna, Emilia Romagna, northern Italy. It dominates the Piazza Maggiore. It is the fifth largest church in the world, stretching for 132 meters in length and 60 in width, while the vault reaches 45 meters inside and 51 meters in the facade. It can contain about 28,000 persons.
The basilica is dedicated to the patron saint of the city, Saint Petronius, who was the bishop of Bologna in the fifth century. The construction was a communal project of Bologna, not of the bishops: The property was a symbol of communal power that was not transferred from the city to the diocese until 1929; the basilica was finally consecrated in 1954. It has been the seat of the relics of Bologna's patron saint only since 2000; until then they were preserved in the Santo Stefano church of Bologna.