Abu Nasr Mansur ibn Ali ibn Iraq (Persian: ابو نصر منصور بن علی بن عراق; c. 960 – 1036) was a Persian Muslim mathematician. He is well known for his work with the spherical sine law.
Abu Nasr Mansur was born in Gilan, Persia, to the ruling family of Khwarezm, the "Banu Iraq". He was thus a prince within the political sphere. He was a student of Abu'l-Wafa and a teacher of and also an important colleague of the mathematician, Al-Biruni. Together, they were responsible for great discoveries in mathematics and dedicated many works to one another.
Most of Abu Nasr's work focused on math, but some of his writings were on astronomy. In mathematics, he had many important writings on trigonometry, which were developed from the writings of Ptolemy. He also preserved the writings of Menelaus of Alexandria and reworked many of the Greeks theorems.
He died in the Ghaznavid Empire (modern-day Afghanistan) near the city of Ghazna.