Aristarchus of Samos was an ancient Greek astronomer and mathematician who flourished around 280 BCE. He was a student of Strato of Lampsacus, connecting him to the Lyceum and the early Hellenistic scientific tradition. Beyond this association, few biographical details survive.

Only one of his works survives complete: On the Sizes and Distances of the Sun and Moon, a geometrical treatise calculating celestial distances from lunar phases. He is most famous for his heliocentric hypothesis, which placed the Sun at the center of the cosmos with a revolving Earth. This revolutionary model is not preserved in his own writings but is reported by later authors like Archimedes and Plutarch.

Aristarchus holds a pivotal place in the history of astronomy for this early heliocentric theory, a radical departure from dominant geocentric models. Though not accepted in antiquity, it was a profound conceptual leap. His surviving work exemplifies the application of rigorous geometry to astronomy, establishing a foundational methodology for later Greek science.