Ahmad Ibn Muhammad Ibn Kathīr Al-farghānī

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī () also known as Alfraganus in the West (870), was an astronomer in the Abbasid court in Baghdad, and one of the most famous astronomers in the 9th century. Al-Farghani composed several works on astronomy and astronomical equipment that were widely distributed in Arabic and Latin and were influential to many scientists.

His best known work, Kitāb fī Jawāmiʿ ʿIlm al-Nujūmi (whose name translates to Elements of astronomy on the celestial motions), was an extensive summary of Ptolemy's Almagest containing revised and more accurate experimental data. Christopher Columbus used Al Farghani's calculations for his voyages to America (but mistakenly interpreted Arabic miles as Roman miles).

In addition to making substantial contributions to astronomy, al-Farghani also worked as an engineer, supervising construction projects on rivers in Cairo, Egypt. The lunar crater Alfraganus is named after him.