Hasan Agha or Hadım Hassan Ağa, also Hassan the eunuch ("Agha" means "Officer"), was a Italian renegade from Sardinia and effective ruler of the Regency of Algiers from 1533 to 1545. He was the deputy (khalifa) 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.
Upon the retirement of Barbarossa in 1544, the son of Barbarossa Hasan Pasha was appointed Governor of Algiers to replace his father, and thus also replace Hasan Agha in the position of effective ruler.
- A history of the Maghrib in the Islamic period by Jamil M. Abun-Nasr p.151ff
- "Leaving the government of Algiers to his khalifa, Hasan Agha, Barbarossa entered Tunisia, seized La Goulette (Aug. 16, 1534) and from there advanced on Tunis." in E.J. Brill's first encyclopaedia of Islam 1913-1936 by M. Th. Houtsma p.872
- Handbook for travellers in Algeria and Tunis, Algiers, Oran, Constantine ... by John Murray (Firm),Sir Robert Lambert Playfair p.38