Abū Bakr ibn Muḥammad ibn al Ḥusayn al-Karajī (c. 953 – c. 1029) was a 10th-century Persian mathematician and engineer who flourished at Baghdad. He was born in Karaj, a city near Tehran. His three principal surviving works are mathematical: "Al-Badi' fi'l-hisab" ("Wonderful on calculation"), "Al-Fakhri fi'l-jabr wa'l-muqabala" ("Glorious on algebra"), and "Al-Kafi fi'l-hisab" ("Sufficient on calculation").