Crateuas was a Greek physician and pharmacologist active in the 1st century BCE. He is specifically identified as a rhizotomist, meaning a specialist in collecting and using medicinal roots and plants. According to later historical sources, he served as the personal physician to King Mithridates VI of Pontus, a ruler famous for his research into poisons and antidotes.

His major work was an illustrated herbal, a book describing medicinal plants. The original text is lost and survives only through fragments and references in the works of later authors, most notably the influential physician Dioscorides. Some scholars believe Crateuas's treatise was among the first to pair detailed plant descriptions with illustrative drawings, a format that became standard in later pharmacological texts.

Crateuas is a significant figure in the history of science as a key link in herbal knowledge between the Hellenistic and Roman periods. His association with the Mithridatic court highlights the political importance of pharmacology and toxicology in the ancient world. Although his own book did not survive, his methods and information were preserved through Dioscorides's work, which remained a central medical text for centuries.