Thucydides, son of Melesias (/θjuːˈsɪdᵻdiːz/; Greek: Θουκυδίδης) was a prominent politician of ancient Athens and the leader for a number of years of the powerful conservative faction. While it is likely he is related to the later historian and general Thucydides, son of Olorus, the details are uncertain; maternal grandfather and grandson fits the available evidence.
Thucydides was born in the deme of Alopeke (Ἀλωπεκή) of Athens. The exact year of his birth is unknown, but his family was noble and he was a relative of Cimon, the charismatic general and leader of the conservative party. After Cimon's death, he succeeded him in the leadership of the conservatives and decided to exert a vehement opposition against Pericles, who was leading Athens at the time.
Thucydides represented the thorough-going conservative party at Athens; their views are most clearly represented by "the Old Oligarch" in his Constitution of the Athenians, which has come down to us among the works of Xenophon.Donald Kagan suggests that Thucydides' ultimate goal, which he could not state openly as doing so would alienate the pro-democratic majority, was to roll back the constitutional changes made by Ephialtes, reinstating the more aristocratic and conservative government that had prevailed in Cimon's day.
Thucydides' political strength reached its peak in the wake of the First Peloponnesian War and the reorganization of the Athenian empire in the early 440s BC. Thucydides developed a new and effective political tactic by having his supporters sit together in the assembly, increasing their apparent strength and giving them a united voice. Kagan asserts that this tactic helped Thucydides mount a concerted opposition to Pericles which brought to light ideological differences among Pericles' supporters.