Hasan Agha or Hadım Hassan Ağa, also Hassan the eunuch, was a Sardinian renegade and effective ruler of the Regency of Algiers from 1533 to 1545. He was the deputy of Hayreddin Barbarossa, who left him in command when he had to leave for Constantinople in 1533. In 1534 also, Hasan Agha continued to be left in command of Algiers when Barbarossa waged his campaigns in Tunisia. Hasan Agha ruled Algiers until 1545, as Barbarossa continued to be based in Istanbul as Commander-in-Chief of the Ottoman fleet. In 1542, he besieged the tribe of the , who had supplied Charles V with 2,000 troops.