The Temple of Isis and Serapis was a double temple in Rome dedicated to the Egyptian deities Isis and Serapis on the Campus Martius, directly to the east of the Saepta Julia. The temple to Isis, the Iseum Campense, stood across a plaza from the Serapeum dedicated to Serapis. The remains of the Temple of Serapis now lie under the church of Santo Stefano del Cacco, and the Temple of Isis lay north of it, just east of Santa Maria sopra Minerva. Both temples were made up of a combination of Egyptian and Hellenistic architectural styles. Much of the artwork decorating the temples used motifs evoking Egypt, and they contained several genuinely Egyptian objects, such as obelisks.
The cult originated in the 1st century BC and the first temple was built in 43 BC, though Augustus and Tiberius tried to ban it as un-Roman. Tiberius destroyed the temple and threw its cult statue into the river Tiber, but his successor Caligula rebuilt it. It was also rebuilt by Domitian after its destruction in the great fire of 80 and in the 3rd century by Severus Alexander. Santo Stefano del Cacco was built on the temple's ruins in the 8th century and its twelve ancient nave columns are from the temple.
Its western entrance was marked by an 11 m wide and 21 m high four-sided triumphal arch from the Saepta Julia, standing at what is now the intersection of Via Pie 'di Marmo and Via del Gesù, that was only demolished at the end of the 19th century. The travertine arch that constituted the eastern entrance was on what is now the Piazza del Collegio Romano. It has also been demolished, but its western pillar is built into the building on the corner of Via del Gesù. Several small obelisks have been excavated nearby and at other locations in Rome, whilst the obelisks for the Fontana del Pantheon, for the Elephant and Obelisk and on the Viale delle Terme are all from the temple.