New Orleans English is American English native to the city of New Orleans and its metropolitan area. Native English speakers of the region actually speak a number of varieties, including the variety most recently brought in and spreading since the 20th century among white communities of the Southern United States in general (Southern U.S. English); the variety primarily spoken by black residents (African-American Vernacular English); the variety spoken by Cajuns in southern Louisiana (Cajun English); the variety traditionally spoken by affluent white residents of the city's Uptown and Garden District; and the variety traditionally spoken by lower middle- and working-class white residents of Eastern New Orleans, particularly the Ninth Ward (sometimes known, since at least the 1980s, as Yat). However, only the last two varieties are unique to New Orleans and are typically those referred to in the academic research as "New Orleans English". These two varieties specific to New Orleans likely developed around the turn of the nineteenth century and most noticeably combine speech features commonly associated with both New York City English and, to a lesser extent, Southern U.S. English. The noticeably New York-like characteristics include the NYC-like short-a split (so that mad and map, for example, do not have the same vowel), non-rhoticity, th-stopping (so that, for example, "those" may sound like "doze"), and the recently disappearing coil–curl merger. Noticeably Southern characteristics include the fronting of /oʊ/ and possible monophthongization of /aɪ/ (just these features, plus non-rhoticity, often characterize the Uptown accent).

Often, the term "Yat" refers particularly to the New Orleans accents that are "strongest" or most especially reminiscent of a working-class New York City accent, though others use the term as a regional marker, to define the speech heard in certain parts of the city and its inner suburbs. Used in these narrower senses, Yat is simply one of many sub-dialects of New Orleans. The word comes from the common use of the local greeting, "Where y'at?" or "Where are you at (i.e. in life)?", which is a way of asking, "How are you?"

A unique New Orleans accent, or "Yat" accent, is considered an identity marker of white metropolitan people who have been raised in the greater New Orleans area. English professor Allan A. Metcalf discusses that "Yats" mostly live near the Irish Channel in blue-collar neighborhoods. The dialect's connotation with the working-class white population therefore encodes the speaker's identities.

The striking similarity between the New Orleans Yat accent and the accent of the New York metropolitan area has been the subject of much speculation. Plausible origins of the accent are described in A. J. Liebling's book The Earl of Louisiana, in a passage that was used as a foreword to A Confederacy of Dunces, John Kennedy Toole's well-known posthumously published novel about New Orleans:

There is a New Orleans city accent ... associated with downtown New Orleans, particularly with the German and Irish Third Ward, that is hard to distinguish from the accent of Hoboken, Jersey City, and Astoria, Long Island, where the Al Smith inflection, extinct in Manhattan, has taken refuge. The reason, as you might expect, is that the same stocks that brought the accent to Manhattan imposed it on New Orleans.

In the decades following the 1803 Louisiana Purchase, when New Orleans changed from being a French colonial possession to an American city, Irish, German, and eventually Italian (largely Sicilian) immigrants indeed began populating the city. However, rather than believing the New York and New Orleans dialects evolved similarly merely due to a similar mixture of European immigrant populations, modern linguists believe that the dialect histories of New Orleans and New York City actually have a direct relationship: significant commercial and demographic interactions between the two cities. Although exact linguistic theories vary, the broad consensus is that key New York accent features probably diffused to New Orleans by the late 19th century. Large-scale movements (permanent or seasonal) of working-class, lower middle-class, and merchant-class Northeastern Americans of European immigrant families to New Orleans may have brought along their native Northeastern (namely, New York City) accent features. Even during the antebellum era, Northerners made up over a quarter of all free, white, non-immigrant residents of New Orleans. Linguist William Labov specifically argues that Jewish American bankers and cotton merchants strongly affiliated with New York City were the biggest influence on upper-class accents (and presumably, the eventual accents of all classes) in New Orleans. He cites examples of Sephardic and German Jewish connections to influential mercantile firms in 19th-century New Orleans.

Many of the features bear a direct relation to Southern American English or New York City English, when not common across the United States more broadly. Of the "Yat" dialect features, the most distinct ones are:

There are some words with phonemic peculiarities, but according to no particular pattern; including 'sink' /ziŋk/, 'room' /ɻʊm/, 'mayonnaise' /ˈmeɪnæz/, 'museum' /mjuˈzɛəm/, 'ask' /æks/.^{[citation needed]}