Candaulism
Candaules, King of Lydia, Shews his Wife by Stealth to Gyges, One of his Ministers, as She Goes to Bed by William Etty. This image illustrates Herodotus's version of the tale of Gyges.
Duke of Orléans Showing His Lover by Eugène Delacroix
"Vashti Refuses the King's Summons" by Edwin Long
Candaulism, also called candaulesism, is a paraphilic sexual practice or fantasy in which one person exposes their naked partner, or images of their naked partner, to other people for their voyeuristic pleasure or the pleasure of their partner. Candaulism is associated with voyeurism and exhibitionism.
The term may also be applied to the practice of undressing or otherwise exposing a partner to others, as well as to either the consensual or non-consensual (and therefore unethical and illegal) posting of personal images of a partner publicly or to urging them to wear clothing which reveals their physical attractiveness to others — such as a microskirt, tight-fitting or see-through clothing, low-cut top, or minimal-coverage swimwear.