Petronius was bishop of Bologna during the fifth century. He is a patron saint of the city. Born of a noble Roman family, he became a convert to Christianity and subsequently a priest. As bishop of Bologna, he built the Church of Santo Stefano.

The Archdiocese of Bologna is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church in Northern Italy. The cathedra is in the cathedral church of San Pietro, Bologna. The current archbishop is Cardinal Matteo Zuppi, who was installed in 2015.