Abu l-Abbas al-Fadl ibn Sahl ibn Zadhanfarukh al-Sarakhsi (died 818), titled Dhu 'l-Ri'āsatayn ("the man of the two commands"), is a famous Persian vizier of the Abbasid era in Khorasan, who serves under Caliph al-Ma'mun (r. 813–832).

He plays a crucial role in the civil war between al-Ma'mun and his brother al-Amin (r. 809–813), and is the de facto ruler of the Caliphate until 817.