San Pietro in Ciel d'Oro (Italian for "Saint Peter in Golden Sky") is a Catholic basilica (and a former cathedral) of the Augustinians in Pavia, Italy, in the Lombardy region.

The paving of the church floor is now lower than the modern street level of Piazza San Pietro in Ciel d'Oro, which lies before its façade.

According to Bede's True Martyrology, the body was removed to Cagliari, Sardinia by the Catholic bishops whom the Arian Vandal Huneric had expelled from north Africa.

An important scriptorium was also built in the monastery in the 9th century and a school, led by the Irish monk Dungal, where, as ordered in the Olonese capitular, issued by the emperor Lothair in the royal palace of Corteolona in 825, they had to go to study students from Milan, Brescia, Bergamo, Lodi, Novara, Vercelli, Tortona, Asti, Acqui, Genoa and Como.

[8] In 1525 the Landsknechte captain Eitel Friedrich III, count of Hohenzollern and Richard de la Pole, pretender to the English crown, who died during the battle of Pavia, were also buried in the basilica.

[9][10] In the 1570s, in compliance with the dictates of the Council of Trent, the numerous sarcophagi and funeral monuments that crowded the basilica were removed, also creating a certain embarrassment during liturgical functions.

A factor complicating the authentication of the remains was that San Pietro in Ciel d'Oro was shared by the two Augustinian religious orders in bitter rivalry.

In 1728, Pope Benedict XIII's intervention in Pavia resulted in his approval of the authenticity of Augustine's bones discovered in the church of San Pietro in Ciel d'Oro.

Compared to the basilica of San Michele Maggiore, one immediately perceives the different proportions of the central nave, wider, longer and less slender, the more rigorous succession of the pillars, all roughly in the same section rather than alternating as in the other church, and the absence of the matronaea.

They brought the saint's relics with them, and in Cagliari they found asylum in an underground chapel, located in largo Carlo Felice, in the Stampace district and accessible by a spiral staircase in the Accardo Palace.

In 722-723 Liutprand probably sent a delegation to Cagliari charged with purchasing the relics with a large sum of money and transporting them to Pavia to bring prestige to the kingdom's new capital.

Having lost track of the original 14th-century burial, around 1360, in the sacristy of the Order of the Augustinian hermits, it was replaced by a candid marble ark, the work of Campionese masters.

[19] Besides being the burial place of Liutprand and Augustine, San Pietro in Ciel d'Oro contains in its crypt that of Boethius, whose Consolation of Philosophy is often taken as the final literary production of Late Antiquity.

")[20] Boccaccio's Decameron features a chapter (tenth day, ninth novella) that takes place in the basilica: the sumptuous bed of Thorello, soundly sleeping, is magically transported to San Pietro in Ciel d'Oro, where the sacristan discovers him at Matins the following morning.