Chalcis (; Ancient Greek & Katharevousa: Χαλκίς, romanized: Chalkís), also called Chalkida or Halkida (Modern Greek: Χαλκίδα, pronounced [xalˈciða]), is the chief city of the island of Euboea or Evia in Greece, situated on the Euripus Strait at its narrowest point. The name is preserved from antiquity and is derived from the Greek χαλκός (copper, bronze), though there is no trace of any mines in the area. In the Late Middle Ages, it was known as Negropont(e), an Italian name that has also been applied to the entire island of Euboea.

Euboea also known by its modern spelling Evia, is the second-largest Greek island in area and population, after Crete, and the sixth largest island in the Mediterranean Sea. It is separated from Boeotia in mainland Greece by the narrow Euripus Strait. In general outline it is a long and narrow island; it is about 180 km (110 mi) long, and varies in breadth from 50 km (31 mi) to 6 km (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 Euboia in the lofty islands of Andros, Tinos and Mykonos.