Ibn al-Muṭahhar al-Ḥillī, al-Ḥasan ibn Yūsuf, 1250-1325

Jamāl ad-Dīn al-Ḥasan ibn Yūsuf ibn ʿAli ibn al-Muṭahhar al-Ḥillī (Arabic: جمال الدين الحسن بن يوسف بن علي بن مطهّر الحلي; December 1250 – December 1325), commonly known as al-Allāmah al-Ḥillī (Arabic: العلامة الحلي, "The Sage of Hillah"), was a Twelver Shi'a Muslim scholar and theologian of Iraqi Arab descent. He is widely regarded as one of the most influential Twelver Shi'i scholars of his time. He was a leading Twelver theologian and an influential early mujtahid in Shiʿi jurisprudence. Later sources retrospectively call him "Ayatollah", though the title originated centuries after his death. According to Al-Hurr al-Amili, his works were enumerated as many as sixty-seven times in bibliographical records. He lived during the time of the Mongol Ilkhanate rule over Iraq and Iran, and significantly influenced the Ilkhan ruler Öljaitü. During the Ilkhanid era, Al-Ḥillī promoted Twelver Shiʿism in Iran. His debates helped convince Öljaitü to convert around 1309–1310, elevating the status of Twelver Shi'ism at court until the Safavids fully established it as the state religion in 1501.