Monseigneur is an honorific

Honorific

An honorific is a word or expression with connotations conveying esteem or respect when used in addressing or referring to a person. Sometimes, the term is used not quite correctly to refer to an honorary title...

 in the French language

French language

French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

. It has occasional English use as well, as it may be a title

Title

A title is a prefix or suffix added to someone's name to signify either veneration, an official position or a professional or academic qualification. In some languages, titles may even be inserted between a first and last name...

 before the name of a French prelate

Prelate

A prelate is a high-ranking member of the clergy who is an ordinary or who ranks in precedence with ordinaries. The word derives from the Latin prælatus, the past participle of præferre, which means "carry before", "be set above or over" or "prefer"; hence, a prelate is one set over others.-Related...

, a member of a royal family

Royal family

A royal family is the extended family of a king or queen regnant. The term imperial family appropriately describes the extended family of an emperor or empress, while the terms "ducal family", "grand ducal family" or "princely family" are more appropriate to describe the relatives of a reigning...

 or other dignitary. Also it is sometimes used as a name for a Frenchman who has a position on the court.

Monsignor

Monsignor

Monsignor, pl. monsignori, is the form of address for those members of the clergy of the Catholic Church holding certain ecclesiastical honorific titles. Monsignor is the apocopic form of the Italian monsignore, from the French mon seigneur, meaning "my lord"...

is both a title and an honorific in the Roman Catholic Church

Roman Catholic Church

The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

. In francophone

Francophone

The adjective francophone means French-speaking, typically as primary language, whether referring to individuals, groups, or places. Often, the word is used as a noun to describe a natively French-speaking person....

 countries, it is rendered Monseigneur, and this spelling is also commonly encountered in Canadian English

Canadian English

Canadian English is the variety of English spoken in Canada. English is the first language, or "mother tongue", of approximately 24 million Canadians , and more than 28 million are fluent in the language...

practice.

The plural form is Messeigneurs.