Sophrosyne (Greek: σωφροσύνη) is an ancient Greek concept of an ideal of excellence of character and soundness of mind, which when combined in one well-balanced individual leads to other qualities, such as temperance, moderation, prudence, purity, and self-control.
In other languages there is no single word that is a simple equivalent, but it is sometimes translated into English as prudence, self-control, moderation, or temperance.
The word is found in the writings of Plato, and its meaning debated in his dialogue Charmides. Plato's high estimation of sophrosyne may have been influenced by Heraclitus's fragment 112, which states: "Sophrosyne is the greatest virtue, and wisdom is speaking and acting the trust, paying heed to the nature of things." (σωφρονεῖν ἀρετὴ μεγίστη, καὶ σοφίη ἀληθέα λέγειν καὶ ποιεῖν κατὰ φύσιν ἐπαίοντας.)
In Greek literature sophrosyne is considered an important quality, and is expressed in opposition to the concept of hubris. A noted example of this occurs in Homer's The Iliad. When Agamemnon decides to take the queen, Briseis, away from Achilles, it is seen as Agamemnon behaving with hubris and lacking sophrosyne. Sophrosyne is a theme in the play Hippolytus by Euripides, where sophrosyne is represented by the goddess Artemis and is personified by the character Hippolytus.
An adjectival form is "sophron".