This thesis studies the role of self-fashioning within the professional practice of ancient physicians and the advancement of medical science. This thesis stems from a desire to appreciate the complex dynamic between medicine and the cultural circumstances of the Greco-Roman world in analyzing antiquity's most accomplished physician Galen. Along with his ostentatious vivisections, Galen's unrelenting targeting of Erasistratus is the most indicative case study of his strategic rhetorical self-fashioning as the king of medicine. Chapter 1 introduces Galen's upbringing and education, outlining the eclectic nature of his medical practice as well as the nature of his desire to become Hippocrates' successor and the medical god Asclepius' descendant. While exploring Hellenistic medicine and the practice of human dissection in Alexandria, Chapter 2 focuses on how Erasistratus' legendary reputation in the Roman imagination as a revolutionary anatomist and love doctor posed the greatest threat to Galen's medical status. Chapter 3 revisits Galen's underlying motives in manufacturing his rivalry with Erasistratus under the framework of the Second Sophistic movement. The chapter culminates with an overview of physiological theories and a careful dissection of Galen's On the Natural Faculties, where his epideictic rhetoric and targeting of Erasistratus come to the fore. Galen resorts to sophistic rhetorical fallacies in dismantling a strawman of Erasistratus, seizing this opportunity to showcase his superiority in usurping his rival. It is an ironic paradox for Galen that his self-fashioning and unrelenting focus in overthrowing his rival are responsible for our knowledge of Erasistratus today.