Pederasty in ancient Greece was a socially acknowledged romantic relationship between an older male (the erastes) and a younger male (the eromenos) usually in his teens. It was characteristic of the Archaic and Classical periods. The influence of pederasty on Greek culture of these periods was so prevalent that it has been called "the principal cultural model for free relationships between citizens."

Some scholars locate its origin in initiation ritual, particularly rites of passage on Crete, where it was associated with entrance into military life and the religion of Zeus. It has no formal existence in the Homeric epics, and seems to have developed in the late 7th century BC as an aspect of Greek homosocial culture, which was characterized also by athletic and artistic nudity, delayed marriage for aristocrats, symposia, and the social seclusion of women. Pederasty was both idealized and criticized in ancient literature and philosophy. The argument has recently been made that idealization was universal in the Archaic period; criticism began in Athens as part of the general Classical Athenian reassessment of Archaic culture.

Scholars have debated the role or extent of pederasty, which is likely to have varied according to local custom and individual inclination. The English word "pederasty" in present-day usage might imply the abuse of minors in certain jurisdictions, but Athenian law, for instance, recognized both consent and age as factors in regulating sexual behavior.