Sant'Agnese fuori la mura ("Saint Agnes Outside the Wall") is a basilica church in Rome, in which Saint Agnes's bones are reputed to rest. The underground area and built a large private mausoleum over it which is now known as the "mausoleo di Santa Costanza" (she was venerated as saint, even though she was not one officially), while the church of Saint Agnes was then built aside. The floor level of the 7th century church is at the level of the catacomb floor, and the public street entrances are at the level of the 2nd floor gallery. Mosaics from the Honorius' edifice are still present. This church was also built with a separate upper gallery for women (matronaeum), similar to that of San Lorenzo fuori le mura. Saint Emerentiana was also buried here.

It is in this church that on the feast day of St. Agnes (January 21), two lambs are specially blessed, usually by the pope after a pontifical high Mass; their wool is later woven into pallia, ceremonial neck-stoles sent by the popes to newly-elevated Metropolitan-archbishops to symbolise their union with the papacy. . The church is currently administrated by a French traditionalist order, the Canons Regular of San Giovanni in Laterano.

A popular local legend says that every lord mayor of Rome secretly comes to pray at this church, on the third night after his election; in fact, there is little evidence that new sindaci really do so.