The Fortress of Kaysun (Turkish: Kaysun Kalesi) is locate near the town of Çakırhüyük in the Adıyaman Province of rural southeastern Turkey. The fortress was a stronghold of the crusader County of Edessa. In 1131, the Danishmend Gümüshtigin besieged the place. Joscelin I, Count of Edessa, hastened to relieve the defenders and died somewhere in the vicinity.