The city of Eretria lies northwest of Chalkis, across from Attic Oropos, in the fertile plain surrounded by the hills of Voudochi to the west and Zervouni to the east. Eretria, the 'rowing city' of the ancient Greeks, named after the verb eretto (=to row), was a great naval force, which had a number of colonies on the coasts of the Aegean, on various islands, and in Italy, since the eighth century BC.

Pottery sherds of the end of the Neolithic period, although not related to specific architectural remains, indicate that the site was inhabited during that period and that it had contacts with the Aegean and the North. In the Early and Middle Helladic periods, the settlement developed in the area between the temple of Apollo Daphnephoros and the agora of the later city, and on the acropolis. The few architectural remains of this early town include a pottery kiln, which demonstrates that industrial activities took place within the settlement. Although limited in number, the finds from the Mycenaean levels suggest a high living standard, confirming references on the Eretrians by Homer in his Catalogue of Ships (Iliad). Even so, Eretria was probably not a major urban centre during this period.

Eretria began to develop a more urban character from the eighth century BC. Temples were established inside the Mycenaean fortified acropolis, and the town's main nucleus was moved to the agora, further south. Eretria participated actively in the first Greek colonization, founding colonies in the North (Pantikapaion and Phanagoreia in the Crimea) and West (Pithikouses in Italy, colonization of Corfu). It also became a major commercial centre with contacts throughout the eastern Mediterranean, as demonstrated by the discovery of Eretrian pottery on the shores of Asia Minor, Syria, and Lebanon, and in Cyprus. Eretria's rapid expansion worried the city of Chalkis, leading the two cities to the so-called Lilantine war (Herodotus 5.99, Thucydides 1.15.3).

Despite the war's negative outcome for Eretria, the city continued to thrive in the Archaic period and participated actively in the second colonization period. Eretria minted its own coins in the last quarter of the sixth century BC and became a democratic state at the end of the sixth century BC. It helped Miletus's revolt against the Persians in 494 BC (Herodotus 6.99, 7.101; Stabo 3.448.5; Pausanias 7.10.2); as a result Miletus was destroyed by Datis and Artaphenes four years later, in 490 BC. The Eretrians fought alongside the Greeks in the naval battle off Artemision and participated in the battles of Salamis and Plataiai. Although initially involved in the First Athenian League, Eretria fought against Athenian hegemony in 411 BC and subsequently thrived economically. It is during this period that the city's fortification wall was strengthened and that new houses and grand public buildings, such as the west gate and theatre, were built. During the fourth century BC, the city was governed by tyrants who invariably sided with either Athens or Thebes.

After the battle of Cheroneia, in 338 BC, Eretria found itself under Macedonian dominion and a new period of economical and cultural prosperity began. The city walls were repaired and extended, new private and public buildings were erected, terracotta workshops were established, and the theatre acquired its final form. The stadium and upper gymnasium were built during this period, together with a second gymnasium or palaestra, which probably included a temple of goddess Eileithea (protector of childbirth), near the port. Stoas were erected along the four sides of the agora, and several monuments (the Tholos being the most noteworthy of these), temples and fountain houses, adorned it. Philoxenos, painter of the panel depicting the battle of Issos, the dramatist Achaios, and the philosopher Menedemos, founder of the Eretrian School, all lived in Eretria. The Macedonian kings Kassandros, Demetrios Poliorketis, and Antigonos Gonatas also spent time in the city. The Romans conquered and destroyed Eretria in 198 BC, which marked the beginning of the city's decline. In 87 BC, Eretria sided with Mithridates, King of Pontus, against the Romans, who destroyed the city for the second time a year later. The city was subsequently abandoned.

Cyriac of Ancona provided the earliest modern account and sketches of ancient Eretria in 1436. Several other early travellers, including Vincenzo Coronelli, William Martin Leake, Charles Robert Cockerell, and Ludwig Ross, visited the area and provided information on the ancient city. The site was first excavated by Christos Tsountas in 1885, followed by the American School of Classical Studies at Athens in 1891-1895. Konstantinos Kourouniotis and, later, I. Papadakis continued the excavations, before the Archaeological Service and the Archaeological Society of Athens took over in the early twentieth century. The Swiss Archaeological School at Athens have excavated the city's west sector, where the temple of Apollo Daphnephoros lies, since 1962.