de rigueur is a French expression that literally means "of rigor" or "of strictness". In English language usage, it means, "necessary according to etiquette, protocol or fashion."

Something that is de rigueur is required by convention or fashion, but not by any hard rule. For example, among the upper classes during the Victorian era, dressing for dinner was de rigueur. In modern times, it is considered de rigueur among many wealthy New York City residents to own a weekend house in the Hamptons.

"De rigueur" is also a type of standard similar to a de facto or a de jure standard. However, unlike de facto or de jure standards, de rigueur standards are more a belief than an actual standard.

Like many other foreign language phrases used in English, it is often italicized when used in a written sentence.

French phrases