Evia οr Euboea is the second-largest Greek island in area and population, after Crete. The narrow Euripus Strait separates it from Boeotia in mainland Greece. In general outline it is a long and narrow, seahorse-shaped island; it is about 180 kilometres (110 mi) long, and varies in breadth from 50 kilometres (31 mi) to 6 kilometres (3.7 mi). Its geographic orientation is from northwest to southeast, and it is traversed throughout its length by a mountain range, which forms part of the chain that bounds Thessaly on the east, and is continued south of Euboea in the lofty islands of Andros, Tinos and Mykonos.
It forms most of the regional unit of Euboea, which also includes Skyros and a small area of the Greek mainland.
The history of the island of Euboea is largely that of its two principal cities, Chalcis and Eretria, both mentioned in the Catalogue of Ships. Both cities were settled by Ionian Greeks from Attica, and would eventually settle numerous colonies in Magna Graecia and Sicily, such as Cumae and Rhegium, and on the coast of Macedonia. This opened new trade routes to the Greeks, and extended the reach of western civilization. The commercial influence of these city-states is evident in the fact that the Euboic scale of weights and measures was used among the Ionic cities generally, and in Athens until the end of the 7th century BC, during the time of Solon. The classicist Barry B. Powell has proposed that Euboea may have been where the Greek alphabet was first employed, c. 775-750 BC, and that Homer may have spent part of his life on the island.
Chalcis and Eretria were rival cities, and appear to have been equally powerful for a while. One of the earliest major military conflicts in Greek history took place between them, known as the Lelantine War, in which many other Greek city-states also took part. Following the infamous battles of Thermopylae and Artemisium, Persian forces captured and sacked Athens, and also took Euboea, Boeotia, and Attica, allowing them to overrun almost all of Greece. In 490 BC, Eretria was utterly ruined and its inhabitants were transported to Persia. Though it was restored nearby its original site after the Battle of Marathon, the city never regained its former eminence.
Both cities gradually lost influence to Athens, which saw Euboea as a strategic territory. Euboea was an important source of grain and cattle, and controlling the island meant Athens could prevent invasion and better protect its trade routes from piracy.
Athens invaded Chalcis in 506 BC and settled 4,000 Attic Greeks on their lands. After this conflict, the whole of the island was gradually reduced to an Athenian dependency. Another struggle between Euboea and Athens broke out in 446. Led by Pericles, the Athenians subdued the revolt, and captured Histiaea in the north of the island for their own settlement.
By 410 BC, the island succeeded in regaining its independence. Euboea participated in Greek affairs until falling under the control of Philip II of Macedon after the Battle of Chaeronea in 338 BC, and eventually being incorporated into the Roman Republic in the second century BC. Aristotle died on the island in 322 BC soon after fleeing Athens for his mother's family estate in Chalcis. From the early Hellenistic period to well into the Roman Imperial period, the island was organized into the Euboean League.
Based on the records of the 2nd century AD geographer Pausanias, it is suspected that the Titan god Crius is an indigenous deity.