Viterbo Cathedral (Italian: Duomo di Viterbo, or Cattedrale di San Lorenzo) is a Roman Catholic cathedral, and the principal church of the city of Viterbo, Lazio, central Italy. It is the seat of the Bishop of Viterbo and is dedicated to Saint Lawrence.
The church is an imposing Romanesque structure situated high on the hill which the city climbs, but it lacks much of the spectacular decoration with which it was originally adorned, thanks to an ill-advised sixteenth-century reconstruction.
According to legend, the cathedral was built on the site of an Etruscan temple of Hercules. Etruscan and Roman foundations can be seen on several of the buildings facing the Piazza di San Lorenzo where the cathedral is situated. Before the 12th century, a parish church dedicated to Saint Lawrence had occupied the site of the cathedral. Even as this church was constructed, the town was already spreading northwards down the hill, leaving the plaza somewhat isolated on the highest edges of town, thus restricting its attraction to the townsfolk, a disadvantage which the local bishops for years attempted to reverse by granting the cathedral special religious privileges.
The cathedral was at the height of its significance during the middle and end of the thirteenth century, when it and the attached Palazzo dei Papi di Viterbo was the home of the papal throne following its flight from Rome and prior to its resettlement in Avignon. Two popes were buried in the duomo: the first was Pope Alexander IV, whose tomb was bizarrely demolished during sixteenth-century renovations, and the location of his remains are now unknown; Pope John XXI is more clearly marked despite several relocations, with a handsome tombstone originally laid over him following his death in 1277 (when his study's ceiling in the papal palace attached to the cathedral suddenly collapsed into the room below due to structural weaknesses as he slept).