9th-century mathematicians by nationality

In the 9th century, notable mathematicians emerged from various cultural and geographical backgrounds, particularly within the Islamic world and Europe. Here's a brief overview by nationality or region: ### Islamic World 1. **Al-Khwarizmi** (Persian) - Often hailed as the "father of algebra," Al-Khwarizmi's works were foundational in developing algebra and introducing the decimal positional number system to the West.