Which Greek mathematician wrote the most definitive text on geometry one that is still referred to today?

The Greek mathematician Euclid wrote the most definitive text on geometry, known as "Elements." This work, composed around 300 BCE, systematically compiled and organized the knowledge of geometry of his time, presenting definitions, postulates, and theorems. Euclid's "Elements" laid the groundwork for modern geometry and continues to be referenced and studied in mathematics education today.