The Battle of Edessa took place between the armies of the Roman Empire under the command of Emperor Valerian and Sassanid forces under Shahanshah (King of the Kings) Shapur I in 259. In this battle, the Sassanids crushed the entire Roman army, while suffering minimal losses.

Prior to the battle, Shapur I had penetrated several times deeply into Roman territory conquering and plundering Antiochia in Syria in 253 or 256. In order to halt these advances and retaliate, Emperor Valerian gathered an army, which included the Roman Praetorian Guard, and marched eastward to the Sassanid borders. He succeeded initially and recaptured Syrian provinces. He then marched to Carrhae and Edessa where he met the main Persian army under command of the King Shapur I. After minor skirmishing with the Persian forces, the main battle commenced.

Shapur I defeated and captured Emperor Valerian, along with many other high ranking officials, though not much is known about the battle itself. The outcome of the battle was an overwhelming Persian victory, with the entire 70,000-strong Roman force being slain or captured. This compared starkly to the minimal number of Persian casualties.

Edessa (Ancient Greek: Ἔδεσσα; Classical Syriac: ܐܘܪܗܝ‎ Urhay; Armenian: Եդեսիա) is the historical name of an ancient town in upper Mesopotamia, refounded on an ancient site by Seleucus I Nicator. For the modern history of the city, see Şanlıurfa.

The earliest name of the city was Adma (Aramaic: אדמא‎ also written Adme, Admi, Admum) which first appeared in Assyrian cuneiforms in the 7th century BCE. A Hellenistic settlement was found on the location of the Assyrian town by Seleucus I Nicator in 304 B.C. The new settlment was named "Edessa" after the ancient capital of Macedonia, perhaps due to its abundant water, just like its Macedonian homonym. The native Syriac name of the city "Orhay" (Classical Syriac: ܐܘܪܗܝ‎) appears to correspond with the toponym Antiochia Kallirhoe "Antioch by the Kallirhoe" (Αντιόχεια η επί Καλλιρρόης), which is found on Edessan coins struck by Antiochus IV Epiphanes (175 - 164 B.C.). The same name appears also in Armenian as Ուռհա, transliterated Urha or Ourha, in Arabic it is الرُّهَا transliterated as Er Ruha or Ar-Ruha, commonly Urfa, and Riha in Kurdish, and in Turkish Urfa, Ourfa, Sanli Urfa, or Şanlıurfa ("Glorious Urfa"), its present name. During Byzantine rule it was named Justinopolis.