Ancient Histria or Istros (Ιστριη, Thracian river god, Danube), was a Greek colony or polis (πολις, city) on the Black Sea coast, established by Milesian settlers to trade with the native Getae. It became the first town on Romanian territory. Scymnus of Chios (ca 110 BC), the Greek geographer and poet, dated it to 630 BC. Eusebius of Caesarea, some centuries later, dated its founding to 657 – 656 BC, at the time of the 33rd Olympic Games. The earliest documented currency on Romanian territory was an 8-gram silver drachma, issued in Histria in the year 480 BC.
 
Archaeological evidence seems to confirm that all trade with the interior followed the foundation of Histria. Traders reached the interior via Histria and the Danube valley, demonstrated by finds of Attic black-figure pottery, coins, ornamental objects, an Ionian lebes and many fragments of amphoras. Amphoras have been found in great quantity at Histria, some imported but some local. Local pottery was produced following establishment of the colony and certainly before mid-6th century. During the archaic and classical periods, when Histria flourished, it was situated near fertile arable land. It served as a port of trade soon after its establishment, with fishing and agriculture as additional sources of income. By 100 AD, however, fishing was almost the sole remaining source of Istrian revenue.
 
Around 30 AD, Histria became a Roman town. During the Roman period from the 1st to 3rd centuries AD, temples were built for the Roman gods, besides a public bath and houses for the wealthy. Altogether, it was in continuous existence for some 14 centuries, starting with the Greek period up to the Roman-Byzantine period. The Halmyris bay where was the city founded was closed by sand deposits and access to the Black Sea gradually was cut. Trade continued until the 6th century AD. The invasion of the Avars and the Slavs in the 7th century AD almost entirely destroyed the fortress, and the Istrians dispersed; the name and the city disappeared.

The ancient Greek city covered around 60 hectares. There are very few written references to the archaic city and archeological research provides the main historical resource. The main deity was Apollo Ietros (The Healer). Zeus (Gr. Polieus) was the protector deity of the city and Aphrodita was also confirmed by archeological research. Historians believe all six Milesian tribes (Greek: phylai) were represented in the colony, yet only four tribes are attested to: the Aigikoreis, Argadeis, Boreis and Geleontes. The only clue concerning the government of the city was given by Aristotle in Politica. Thanks to his comment, it is clear that the first government of Histria was an oligarchy. From an economic point of view, the town was developed around port-related activities.

During the Hellenistic period, there was continuity in the cult of Apollo Ietros, Zeus (Gr. Polieus) and Aphrodita. A new temple for a grand deity was built. There is also evidence of the cult of Athena, Poseidon, Helikonios, Taurios, Demetra, Hermes Agoraios, Heracles, Asclepios, Dioscurii and others. A new wall also appears, protecting a 10 ha area. During the Hellenistic period Histria had become an important supplier of grain for Greece.[5] However, the economic power of Histria was represented by trade.[6] In the Hellenistic period, the gymnasium and the theater were erected.

During the classical period, there was continuity in the cults of Apollo Ietros; Zeus (Gr. Polieus) and Aphrodita. A new wall with a single tower was erected. During the classical period many written sources describe the political organisation of the area. The Odrysian kingdom was involved in fighting with the Scythians ruled by Ariapeithes and Histria was situated between the two kingdoms. Due to that, most probably, Histria town was forced to join the Delian League. In the 5th century BC, these colonies were under the influence of the Delian League, passing in this period from oligarchy to democracy[3] From an economic point of view it was during this era that the first Histrian coins were minted: a didrachma, oboli and bronze coins.