The plague of Athens raged for 4 years and resulted in the defeat of Athens. The cause of the plague of Athens continues to be debated. Infectious diseases most often cited as causes of the plague include influenza, epidemic typhus, typhoid fever, bubonic plague, smallpox, and measles. Thucydides provides the only available description of the plague of Athens. Given the nuances of the translation, bubonic plague, smallpox, and measles are the most likely causes of the plague. In my view, measles is the most likely cause of the plague of Athens.