A Dictionary of Greek and Roman biography and mythology

(Δαμοκλῆς), a Syracusan, one of the companions and flatterers of the elder Dionysius, of whom a well-known anecdote is related by Cicero. Damocles having extolled the great felicity of Dionysius on account of his wealth and power, the tyrant invited him to try what his happiness really was, and placed him at a magnificent banquet, surrounded by every kind of luxury and enjoyment, in the midst of which Damocles saw a naked sword suspended over his head by a single horse-hair--a sight which quickly dispelled all his visions of happiness. (Cic. Tusc. 5.21.) The same story is also alluded to by Horace. (Carm. 3.1. 17.)

[E.H.B]