Abū al-Wafāʾ, Muḥammad ibn Muḥammad ibn Yaḥyā ibn Ismāʿīl ibn al-ʿAbbās al-Būzjānī (10 June 940 – 15 July 998) is a Persian mathematician and astronomer who works in Baghdad.

He makes important innovations in spherical trigonometry, and his work on arithmetic for businessmen contains the first instance of using negative numbers in a medieval Islamic text.

He is also credited with compiling the tables of sines and tangents at 15' intervals.

He also introduces the sec and cosec functions, as well studies the interrelations between the six trigonometric lines associated with an arc.

His Almagest is widely read by medieval Arabic astronomers in the centuries after his death.

He is known to have written several other books that have not survived.