Seleucia was the capital of the Seleucid Empire under Seleucus I.
Seleucus I Nicator founded Seleucia on the Tigris around 305 BCE, shortly after the death of Alexander the Great and the division of Alexander’s empire among his successors. The city stood near Babylon and was positioned to control important routes through Mesopotamia. It quickly became one of the largest urban centers in the Hellenistic world.
Seleucia combined Greek and Mesopotamian traditions. Greek institutions and settlers were present, while the city’s location connected it to older Babylonian economic and cultural networks. It served as the principal royal center of the early Seleucid kings, although the empire also had important western capitals, including Antioch.
The city later declined as political power shifted toward Ctesiphon under the Parthians. Its remains are associated with the archaeological site of Tell Umar in modern Iraq. Seleucia is sometimes confused with Babylon, which remained a major ancient city, or Antioch, which became the most prominent Seleucid center in the western part of the empire.