Jawdhar (Arabic: جوذر, before 909 – March 973), surnamed al-Ustadh (Arabic: الأستاذ, lit. 'the Master'), was a eunuch slave who served the Fatimid caliphs al-Qa'im, al-Mansur, and al-Mu'izz as chamberlain and de facto chief minister until his death. He was an extremely powerful figure in the Fatimid court, and was ranked immediately after the caliph and his designated heir. The accession of al-Mansur was probably due to Jawdhar's machinations, and he was placed in charge of keeping the new caliph's relatives under house arrest. He enjoyed close relations with the Kalbid emirs of Sicily, which enabled him to engage in profitable commerce with the island. Jawdhar accompanied al-Mu'izz during the migration of the court from Ifriqiya to Egypt, but died on the way at Barqa. His collected documents and letters were published after his death by his secretary as the Sirat al-Ustadh Jawdhar, and form one of the main historical sources for the governance of the Fatimid state in the period.