Nasr ibn Abdallah, known as Kaydar (Arabic: كيدر نصر بن عبد الله; nisbah given variously as al-Safadi الصفدي or al-Sughdi الصغدي) was a governor of Egypt for the Abbasid Caliphate, serving there from 832 until his death in 834.
In 833 Kaydar received a letter from al-Ma'mun's brother and successor Abu Ishaq, announcing the formation of the mihnah and instructing him to implement it in Egypt.
He accordingly questioned the qadi Harun ibn Abdallah al-Zuhri, along with other officials and legal experts, and received their affirmation of the createdness of the Qur'an.
The new caliph wrote to Kaydar, ordering him to drop the names of the provincial Arabs from the army registers (diwan) and stop paying their salaries.
This act met stiff resistance, however, and soon a certain Yahya ibn al-Wazir al-Jarawi revolted and drew five hundred men to his cause.