3rd-century BC astronomers

Eratosthenes of Cyrene ( ; ;  – ) was an Ancient Greek polymath: a philosopher, scholar, mathematician, geographer, poet, astronomer, and music theorist. Eratosthenes eventually became the chief librarian at the Library of Alexandria. His work was the precursor to the modern discipline of geography, and he introduced some of its terminology, coining the terms geography and geographer.

thumb| Berossus () or Berosus (; ; possibly derived from ) was an early-3rd-century BCE Hellenistic-era Babylonian writer, priest of Bel Marduk, and astronomer who wrote in the Koine Greek language.

Sudines (or Soudines) () () was a Babylonian sage. He is mentioned as one of the famous Chaldean mathematicians and astronomer-astrologers by later Roman writers like Strabo (Geographia 16:1–6).