Herophilos, sometimes Latinized Herophilus (335-280 BC), was a Greek physician. He was born in Chalcedon in Asia Minor (now Kadiköy, Turkey). He is known as the first anatomist in history. Together with Erasistratus he is regarded as a founder of the great medical school of Alexandria. He was the first to base his conclusions on dissection of the human body. He studied the brain, recognizing it as the center of the nervous system and the site of intelligence. He also paid particular attention to the nervous system, distinguishing nerves from blood vessels and the motor from the sensory nerves. Other areas of his anatomical study include the eye, liver, pancreas and the alimentary tract as well as the salivary and genital organs. His works were lost but were much quoted by Galen in the 2nd century AD.

Another figure by this name (Herophilus) was an imposter in the time of Julius Caesar who pretended to be the grandson of Marius. Caesar banished him for sedition, and he was later strangled in prison.