Paestum was a major ancient Greek city on the coast of the Tyrrhenian Sea in Magna Graecia. The ruins of Paestum are famous for their three ancient Greek temples in the Doric order ( The first Temple of Hera, the second Temple of Hera & the Temple of Athena) dating from about 600 to 450 BC, which are in a very good state of preservation. The city walls and amphitheatre are largely intact, and the bottom of the walls of many other structures remain, as well as paved roads. The site is open to the public, and there is a modern national museum within it, which also contains the finds from the associated Greek site of Foce del Sele.

In the central part of the complex is the Roman Forum, thought to have been built on the site of the preceding Greek agora. On the north side of the forum is a small Roman temple, dated to 200 BC. It was dedicated to the Capitoline Triad, Juno, Jupiter, and Minerva. To the north-east of the forum is the amphitheater.

According to Strabo the city was founded as Poseidonia (named after the Greek deity of the sea) by Greek Achaeans from Sybaris. The colonists had built fortifications close to the sea, but then decided to found the city farther inland at a higher elevation.