Alī ibn Aḥmad al-Nasawī (c. 1011 possibly in Khurasan – c. 1075 in Baghdad) was a Persian^[1] mathematician from Khurasan, Iran. He flourished under the Buwayhid sultan Majd al-dowleh, who died in 1029-30AD, and under his successor. He wrote a book on arithmetic in Persian, and then Arabic, entitled the "Satisfying (or Convincing) on Hindu Calculation" (al-muqni fi-l-hisab al Hindi). He also wrote on Archimedes's Book of Lemmas and Menelaus's theorem (Kitab al-ishba, or "satiation"), where he made corrections to the Book of Lemmas as translated into Arabic by Thabit ibn Qurra and last revised by Nasir al-Din al-Tusi.

Al-Nasawī's arithmetic explains the division of fractions and the extraction of square and cubic roots (square root of 57,342; cubic root of 3, 652, 296) almost in the modern manner. Al-Nasawī replaces sexagesimal by decimal fractions.

Al-Nasawī criticises earlier authors, but in many cases incorrectly. His work was not original, and he sometimes writes of matters that he does not understand, e.g. "borrowing" in subtraction.^[2]

Ragep and Kennedy also give an analysis of a mid-12th-century manuscript in which a summary of Euclid's Elements exists by al-Nasawī.