Edessa was an ancient city (polis) located in Upper Mesopotamia, situated in the region that is currently known as Urfa or Şanlıurfa, Turkey. It was established during the Hellenistic period by Seleucus I Nicator, a Macedonian general and founder of the Seleucid Empire. The city was named after an ancient Macedonian capital, with its Greek name meaning "tower in the water."
Throughout its history, Edessa served as a significant administrative center, acting as the capital for the Kingdom of Osroene and subsequently the Roman province of Osroene. During Late Antiquity, it became a notable hub for Christian learning and served as the seat of the Catechetical School of Edessa. Additionally, during the Crusades, the city functioned as the capital of the County of Edessa.