Abū Muḥammad Jābir b. Aflaḥ al-Ishbīlī or al-Andalusī was a mathematician and theoretical astronomer who lived most likely in Seville during the first half of the sixth/twelfth century. Virtually nothing is known about his life, but his chronology seems well established due to the fact that: 1) Maimonides (d. 601/1204; Guide , 268-9) says that he was acquainted with Jābir's son; 2) According to Ibn al-Qifṭī (d. 645/1248), Joseph ben Yehudah ben Shamʿūn (d. 623/1226) brought Jābir's Iṣlāḥ al-Majisṭī ("Revision