Settlers from two cities in Euboea, Greece, jointly colonised the nearby Cumae, the earliest Greek site on mainland Italy. The earliest founding of Naples itself is claimed in legend to be the Greek colony Phál?ron (Latinized form: Phalerum), after the hero Phál?ros, an Argonaut in Greek mythology. Parthenóp? was named after the siren in Greek mythology said to have washed ashore at Megaride after throwing herself into the sea when she failed to bewitch Ulysses with her song. Around this time Greeks became locked in a power struggle with the Etruscans, who sought to dominate the area. Etruscans attacked Cuma and, although the attack failed, it signaled a growing Etruscan determination to dominate the area, the pressure of which pushed Parthenope to the commercial margins. There is evidence that the city had slid into decadence and, some argue, had virtually ceased to exist.
Once Etruscan influence had weakened around the mid-400s BC, the area was occupied by settlers from the nearby Greek colony of Cumae, who rebuilt somewhat inland, where they founded Neápolis ("New City" in Greek). The original Parthenope came to be called simply the "Old City", Palaípolis. The two separate cities had grown into a single conurbation by the 3rd century BC. Neapolis had a powerful line of walls, in front of which the Carthaginian invader Hannibal had to retreat when the city was allied with the Romans. Other features were an odeon and a theatre, and the temple of the city's patron gods, the Dioscuri or Divine Twins Castor and Pollux. Although conquered by the Samnites during the fifth century B.C.,[8] and then the Romans, Naples long retained its Greek culture; it is significant that modern Neapolitans still refer to themselves often as Partenopéi, "Parthenopeans".
In the Roman era the city was a flourishing centre of Hellenistic culture that attracted Romans wanting to perfect their knowledge of Greek culture. The pleasant climate made it a renowned pleasure resort, as recounted by Virgil and manifested by the number of luxurious villas that dotted the coast from the Gulf of Pozzuoli to the Sorrentine peninsula. The famous district of Posillipo takes is name from the ruins of Villa Pausílypon, meaning, in Greek, "a pause, or respite, from worry". Romans connected the city to the rest of Italy with their famous roads, excavated galleries to link Naples to Pozzuoli, enlarged the port, and added public baths and aqueducts to improve quality of life in Naples. The city was also celebrated for its many feasts and spectacles.
According to legend, the Saints Peter and Paul themselves came to the city to preach. Christians had a prominent role in the late years of the Roman Empire, and there are several notable catacombs, especially in the northern part of the city. The first palæo-Christian basilicas were built next to the entrances to the catacombs. The greatly popular patron of the city, San Gennaro (St. Januarius), was decapitated in nearby Pozzuoli in 305 AD, and since the 5th century he is commemorated by the basilica of San Gennaro extra Moenia. The Cathedral of Naples is also dedicated to St. Gennaro.
It was in Naples, in Lucullus' Villa in what is now the Castel dell'Ovo, that Romulus Augustulus, the last nominal Emperor of the West, was imprisoned after being deposed in 476. Naples suffered much during the Gothic Wars between Ostrogoths and Byzantines in the 6th century: in 542 it fell to the troops of Totila but not much later became Greek once again. When the Lombards invaded and conquered much of Italy in the following years, Naples remained loyal to the Byzantine Empire.