Harmodios (c. 530-514 BC) and Aristogeiton (c. 550-514 BC), known as "the Liberators" and "the Tyrannicides", became heroes in Athens through their role in the overthrow of the Tyranny of the Peisistratid family, specifically the slaying of Hipparkhos. They were the first two Ancient Greeks considered by their countrymen worthy of having statues raised to them.
Ironically, modern scholarship has concluded that Hipparkhos was not a tyrant, but that his brother Hippias was, and actually become a cruel ruler after the death of Hipparkhos. Only after Hippias was overthrown were Harmodios and Aristogeiton lionized, and Hipparkhos described as a tyrant.
When Alkibiades took Athens, Kritias publically denounced him as a tyrant while standing near the statues of Harmodios and Aristogeiton. He was promptly stabbed to death. Shortly after, Sokrates stood near the same spot to denounce Alkibiades as well, even though he knew he was signing his own death-warrant.
Mithredath and Polydoros found the base of a statue in the ruins of the Athenian marketplace. Polydoros translated the inscription as "Harmodios and Aristogeiton, those who slew the tyrant Hipparkhos". Polydoros explained that a tyrant was a ruler of a city who was not of a kingly line. Mithredath thought it was madness for a city to honour the slayers of a ruler.