Euboea is the second largest Greek island in area and population, after Crete
Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...

. The narrow Euripus Strait
Euripus Strait
The Euripus Strait , is a narrow channel of water separating the Greek island of Euboea in the Aegean Sea from Boeotia in mainland Greece. The strait's principal port is Chalcis on Euboea, located at the strait's narrowest point....

 separates it from Boeotia
Boeotia, also spelled Beotia and Bœotia , is one of the regional units of Greece. It is part of the region of Central Greece. It was also a region of ancient Greece. Its capital is Livadeia, the second largest city being Thebes.-Geography:...

 in mainland Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

. In general outline it is a long and narrow, seahorse-shaped island; it is about 150 kilometres (93.2 mi) long, and varies in breadth from 50 kilometres (31.1 mi) to 6 kilometres (3.7 mi). Its general direction 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
Thessaly is a traditional geographical region and an administrative region of Greece, comprising most of the ancient region of the same name. Before the Greek Dark Ages, Thessaly was known as Aeolia, and appears thus in Homer's Odyssey....

 on the east, and is continued south of Euboea in the lofty islands of Andros
Andros, or Andro is the northernmost island of the Greek Cyclades archipelago, approximately south east of Euboea, and about north of Tinos. It is nearly long, and its greatest breadth is . Its surface is for the most part mountainous, with many fruitful and well-watered valleys. The area is...

, Tinos
Tinos is a Greek island situated in the Aegean Sea. It is located in the Cyclades archipelago. In antiquity, Tinos was also known as Ophiussa and Hydroessa . The closest islands are Andros, Delos, and Mykonos...

 and Mykonos
Mykonos is a Greek island, part of the Cyclades, lying between Tinos, Syros, Paros and Naxos. The island spans an area of and rises to an elevation of at its highest point. There are 9,320 inhabitants most of whom live in the largest town, Mykonos, which lies on the west coast. The town is also...

Like most of the Greek islands, Euboea was originally known under other names in ancient times
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, such as Macris and Doliche from its shape, Ellopia and Abantis from the tribes inhabiting it.

Euboea was believed to have originally formed part of the mainland, and to have been separated from it by an earthquake.