Plural of “monsieur”

The plural of monsieur is messieurs.

Why

"Monsieur" is French for "my lord" (from "mon" plus "sieur," an older form of "seigneur"), used as a polite title before a man's name or on its own as a form of address, much like "Mister" or "sir" in English. English borrowed the word intact for describing French men specifically, and it kept its genuinely irregular French plural, "messieurs," rather than adopting a regularized English form, since the plural is almost always used in a specifically French or French-flavored context where the original form feels appropriate.

Unlike "adieu," "monsieur" has essentially no competing anglicized plural in circulation — you will not find "monsieurs" used seriously in edited English prose — because the word functions as a direct title borrowed for use in French settings or when addressing French men, and it would feel like a genuine error rather than a stylistic choice to invent an English-style plural for it.

Usage note

"Messieurs" (pronounced meh-SYUR) is used mainly in formal address ("Messieurs, please be seated") or in writing describing multiple Frenchmen referred to by title, and it appears far more rarely in everyday English than "adieu" does, since it's tied specifically to referring to or addressing French men rather than being a general-purpose word.

The abbreviation "MM." (doubling the single abbreviation "M." for monsieur) is the standard written short form for "messieurs" in French and in English writing that follows French convention, similar to how "pp." doubles a single-letter Latin abbreviation for a plural sense. "Messieurs" also appears occasionally in English-language business or diplomatic correspondence addressed to French counterparts, following French epistolary convention exactly, which is another reason the word has never regularized — anyone using it in English is almost always deliberately invoking French formality rather than treating it as a naturalized English noun.

Common real mistakes

Writers unfamiliar with French sometimes attempt to pluralize "monsieur" as "monsieurs," which is a genuine error rather than an accepted variant — the plural is irregular and must be "messieurs," a completely different word form, not a suffix added to the singular.

The wider pattern

Alongside "adieu," "monsieur" shows how French terms of address and set phrases, when borrowed into English for use specifically in French or French-flavored contexts, tend to keep their original irregular plurals far more rigidly than French common nouns like "bureau" or "plateau," which regularize toward English -s the more they're used in ordinary English speech. "Madame" and "mademoiselle," the corresponding French titles for women, follow entirely different and more regular pluralization patterns in French itself ("mesdames," "mesdemoiselles"), and English borrows all three titles as needed in French-flavored writing, though "monsieur/messieurs" is by far the most commonly encountered of the group in English-language fiction and journalism about France.

Examples

• The waiter addressed the messieurs at the corner table with a slight bow.
• Several messieurs from the delegation arrived a day early.
• The letter began, 'Messieurs, we regret to inform you...'
• Two messieurs debated the wine list for several minutes.
• The memoir describes the messieurs who frequented her grandfather's café.
• Messieurs of the committee were asked to submit their votes in writing.
• The old photograph shows three messieurs posing stiffly for the camera.
• She recalled the messieurs who used to gather at the same table every evening.
• The play's opening scene introduces the messieurs one by one.
• Historical records name the messieurs who signed the original charter.
• The ambassador greeted the messieurs individually before the summit began.
• Old ledgers list the messieurs who financed the original railway.
• Several messieurs objected loudly to the proposed terms.
• The historical drama features messieurs debating politics late into the night.
• The play's cast included several messieurs from the local theater troupe.
• Letters addressed to the messieurs were kept in a separate file.
• The historical account names the messieurs present at the treaty signing.
• Two messieurs argued loudly about the wine before the meal even began.