Saint Lawrence outside the Walls (San Lorenzo fuori le mura) is a basilica in Rome. It takes its origins from a small oratory built by the Emperor Constantine over the martyr's burial place in 330; the building was remodelled by Pope Pelagius II around 580. Sixtus built a church dedicated to the Virgin abutting that of St Lawrence circa 435. In the thirteenth century, Pope Honorius III united the two buildings as part of a programme of urban renewal; the frescos depicting the life of Saint Lawrence and of Saint Stephen inside the portico are from this period. The church was bombed during 1943; the restoration lasted from 1943 to 1948, allowing some nineteenth-century accretions to be removed.

Besides St Lawrence, Pope Pius IX is also buried in the church.