Abu Amir Yusuf ibn Ahmad ibn Hud;
(Arabic: أبو عامر يوسف إبن أحمد إبن هود, romanized: Abū ʿĀmir Yūsuf ibn Aḥmad ibn Hūd; died c. 1085), known by his regnal name al-Mu’taman Billah (Arabic: المؤتمن بالله, romanized: al-Mūʿtaman bi-‘llāh, lit. ‘Trustee through God’), was the third king of the Banu Hud dynasty who ruled over the Taifa of Zaragoza from 1081 to 1085.
Yusuf al-Mu’taman reigned during the height of power of Muslim Zaragoza, following the thriving period of his father Ahmad al-Muqtadir. He continued his father’s efforts and created around him a court of intellectuals, living in the beautiful palace of Aljafería, nicknamed as “the palace of joy”.
Al-Mu’taman was also a scholarly king and a patron of science, philosophy and arts. He knew astrology, philosophy, and especially mathematics, a discipline in which he wrote the most important treatise from al-Andalus, the Kitab al-Istikmal (“Book of Perfection”).