Looking to rank the legendary physician and philosopher who shaped Western medicine for over a millennium? This ranking explores Galen of Pergamon's contributions, influence, and lasting impact on medical science. From his groundbreaking anatomical discoveries through animal dissection to his theory of the four humors that dominated medical thinking for 1,500 years, Galen's work represents a pivotal bridge between ancient Greek medicine and the Renaissance. Whether evaluating his surgical innovations, his philosophical writings, or his role as physician to Roman emperors, this assessment examines why Galen remains one of history's most influential medical figures—despite some theories that were later proven incorrect.