Role Mathematician Name Al Nayrizi | Died 922 AD, Baghdad, Iraq | |

**Abū’l-‘Abbās al-Faḍl ibn Ḥātim al-Nairīzī** (Arabic: أبو العباس الفضل بن حاتم النيريزي, Latin: *Anaritius, Nazirius*, 865–922) was a Persian mathematician and astronomer from Nayriz, Fars Province, Iran.

He flourished under al-Mu'tadid, Caliph from 892 to 902, and compiled astronomical tables, writing a book for al-Mu'tadid on atmospheric phenomena.

Nayrizi wrote commentaries on Ptolemy and Euclid. The latter were translated by Gerard of Cremona. Nairizi used the so-called umbra (versa), the equivalent to the tangent, as a genuine trigonometric line (but he was anticipated in this by al-Marwazi).

He wrote a treatise on the spherical astrolabe, which is very elaborate and seems to be the best Persian work on the subject. It is divided into four books:

- Historical and critical introduction.
- Description of the spherical astrolabe; its superiority over plane astrolabes and all other astronomical instruments.
- Applications.
- Applications.

He gave a proof of the Pythagorean theorem using the Pythagorean tiling.

Ibn al-Nadim mentions Nayrizi as a distinguished astronomer with eight works by him listed in his book *al-Fihrist*.