Poseidonia
| Poseidonia Ποσειδωνία | |
|---|---|
| Coordinates: 37°23′N 24°53′E / 37.383°N 24.883°E | |
| Country | Greece | 
| Administrative region | South Aegean | 
| Regional unit | Syros | 
| Municipality | Syros-Ermoupoli | 
| Area | |
| • Municipal unit | 23.7 km2 (9.2 sq mi) | 
| Population  (2021) | |
| • Municipal unit | 4,114 | 
| • Municipal unit density | 170/km2 (450/sq mi) | 
| • Community | 967 | 
| Time zone | UTC+2 (EET) | 
| • Summer (DST) | UTC+3 (EEST) | 
| Vehicle registration | EM | 
Poseidonia (Greek: Ποσειδωνία, romanized: Posidonía, named after Poseidon) is a village and a former municipality on the island of Syros, in the Cyclades, Greece. Since the 2011 local government reform it is part of the municipality Syros-Ermoupoli, of which it is a municipal unit. The population was 4,114 inhabitants at the 2021 census, and the land area is 23.705 km². The municipal unit shares the island of Syros with the municipal units of Ano Syros and Ermoupoli. It is also known as Dellagrazia (name taken from a small church of Maria della Grazia).