Pederasty in ancient Greece was a socially acknowledged relationship between an adult male and a younger male usually in his teens. It was characteristic of the Archaic and Classical periods. 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.

The social custom called paiderastia by the Greeks was both idealized and criticized in ancient literature and philosophy; it has no formal existence in the Homeric epics, and seems to have developed in the late 7th century BCE 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. The influence of pederasty was so pervasive that it has been called "the principal cultural model for free relationships between citizens."

Scholars have debated the role or extent of sexual activity, which is likely to have varied according to local custom and individual inclination. The English word "pederasty" in present-day usage implies the abuse of minors, but Athenian law, for instance, did not recognize consent and age as factors in regulating sexual behavior. As classical historian Robin Osborne has pointed out, historical discussion of paiderastia is complicated by 21st-century moral standards: