The Diocese of Tortona is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Northern Italy, spanning parts of three regions of Piedmont, Lombardy and Liguria. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Genoa and forms part of the ecclesiastical region of Liguria. The diocese claims to be one of the oldest in Lombardy and the Piedmont.

The Archdiocese of Genoa is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Italy. Erected in the 3rd century, it was elevated to an archdiocese on 20 March 1133. The archdiocese of Genoa was, in 1986, united with the Diocese of Bobbio-San Colombano, forming the Archdiocese of Genoa-Bobbio; however a split in 1989 renamed it the "Archdiocese of Genoa."