The Porta San Paolo is among the most majestic and best preserved of the entire circle of the Aurelian Wall.

Originally two gates were built flanking the Pyramid Cestia, built to facilitate the many trades between the Urbe and the port of Ostia. The western gate that stretched towards the granaries of the Marmorata, on the banks of the Tiber, was later closed because of the better connection via the Via Portuense and was demolished in 1888. The original name of the surviving gate was Porta Ostiensis, because the via Ostiense, the connecting road between the Urbe and the ancient port of Ostia, started there. The Porta's fundamental role then faded with the loss of importance of the port itself. It was later renamed Porta San Paolo for the exit towards the Basilica of St Paul Outside the Walls.

Between 401 and 403, the Gate was renovated by Emperor Honorius, who proceeded to maintain a single entrance archway, reinforcing and raising the two side towers, and fitting them with battlements and windows. Inside the so-called Castelletto, the counter-door similar to a small fortification built by Maxentius at the beginning of the 4th century A.D., is currently housed the Museum of the Via Ostiense of the Special Superintendence of Rome, where reconstructions of the ports of Ostia and the monuments found along the Via Ostiensis are exhibited.

Among the many restorations, we would like to mention the fundamental one from the time of Benedict XIV (1749), who had the entire Roman city walls restored, starting from the Porta San Paolo to the Porta Flaminia, remembered with a commemorative inscription on the eastern tower. Around 1920 the gate was isolated from the Aurelian Wall to facilitate traffic in the adjacent area on the eastern side. Later, due to bombing during the Second World War, the western section of the wall, which connected it to the Cestia pyramid, was also destroyed. On 10 September 1943, Porta San Paolo was the scene of the last attempt by the Italian army and Roman civilians to avoid the German occupation of Rome.