Edessa (/ɪˈdɛsə/; Ancient Greek: Ἔδεσσα, romanized: Édessa) was an ancient city (polis) in Upper Mesopotamia, founded during the Hellenistic period by King Seleucus I Nicator (r. 305–281 BC), founder of the Seleucid Empire. It later became capital of the Kingdom of Osroene, and continued as capital of the Roman province of Osroene. In Late Antiquity, it became a prominent center of Christian learning and seat of the Catechetical School of Edessa. During the Crusades, it was the capital of the County of Edessa.