Erétria (Greek: Ερέτρια, literally "city of the rowers") was a polis in Ancient Greece, located on the western coast of the island of Euboea, south of Chalcis, facing the coast of Attica across the narrow Euboean Gulf. Eretria was an important Greek polis in the 6th/5th century BC. However, it lost its importance already in antiquity. Excavations of the ancient city began in the 1890s and have been conducted since 1964 by the Greek Archaeological Service (11th Ephorate of Antiquities) and the Swiss School of Archaeology in Greece. Today, there is a modern Greek town of the same name on the ancient site.
The first known settlement from the Early Helladic period (3000-2000 BC) was located in the plain. A granary and several other buildings as well as a pottery kiln have been found so far. This settlement was moved to the top of the Acropolis in the Middle Helladic period (2000-1600 BC), because the plain was flooded by the nearby lagoon. In the Late Helladic period (1600-1100 BC), the population dwindled and the remains found so far have been interpreted as an observation post. The site was abandoned during the Dark Ages.