Xenia is the ancient Greek concept of hospitality, the generosity and courtesy shown to those who are far from home and/or associates of the person bestowing guest-friendship. The rituals of hospitality created and expressed a reciprocal relationship between guest and host expressed in both material benefits as well as non-material ones .
The Greek god Zeus is sometimes called Zeus Xenios in his role as a protector of travelers. He thus embodied the religious obligation to be hospitable to travelers. Theoxeny or theoxenia is a theme in Greek mythology in which humans demonstrate their virtue or piety by extending hospitality to a humble stranger (xenos), who turns out to be a disguised deity (theos) with the capacity to bestow rewards. These stories caution mortals that any guest should be treated as if potentially a disguised divinity and help establish the idea of xenia as a fundamental Greek custom. The term theoxenia also covered entertaining among the gods themselves, a popular subject in classical art, which was revived at the Renaissance in works depicting a Feast of the Gods.
Xenia consists of two basic rules:
Xenia was considered to be particularly important in ancient times when people thought gods mingled among them. If one had poorly played host to a stranger, there was the risk of incurring the wrath of a god disguised as the stranger. It is thought that the Greek practice of theoxenia may have been the antecedent of the Roman rite of Lectisternium, or the draping of couches.
While this particular origin of the practices of guest-friendship are centralized around the divine, however, it would become common practice among the Greeks to incorporate xenia into their customs and manners for very much all of ancient Greek history. Indeed, while originating from mythical traditions, xenia would very much become a standard practice throughout much (if not, all) of Greece as customarily proper in the affair of men interacting with men as well as men interacting with the Gods.