Quis custodiet ipsos custodes?

Quis custodiet ipsos custodes? is a Latin phrase found in the Satires (Satire VI, lines 347–348), a work of the 1st–2nd century Roman poet Juvenal. It may be translated as "Who will guard the guards themselves?" or "Who will watch the watchmen?".

The original context deals with the problem of ensuring marital fidelity, though the phrase is now commonly used more generally to refer to the problem of controlling the actions of persons in positions of power, an issue discussed by Plato in the Republic.[citation needed] It is not clear whether the phrase was written by Juvenal, or whether the passage in which it appears was interpolated into his works.