The Resian dialect or simply Resian (self-designation Standard Rozajanski langäč / Rozojanski langäč, Bila Rozajanski langäč / Rozojanski langäč, Osoanë Rozoanske langäč, Solbica Rozajonski langeč / Rozojonski langeč; Slovene: rezijansko narečje [ɾɛziˈjáːnskɔ naˈɾéːt͡ʃjɛ], rezijanščina; Italian: Dialetto Resiano) is a distinct variety in the South Slavic continuum, generally considered a Slovene dialect spoken in the Resia Valley, Province of Udine, Italy, close to the border with Slovenia.

Together with the Rosen Valley dialect and Ebriach dialect in Carinthia, it is one of the three dialects of Slovene spoken entirely outside the borders of Slovenia. It is unequivocally one of the most distinct and difficult dialects to understand for speakers of central Slovene dialects, especially because most Resians are not familiar with standard Slovene. Its distinguishing characteristic is centralized, breathy vowels. It borders the Slovene Torre Valley dialect to the south and the Soča dialect to the east, both separated by tall mountain ranges. On the other sides, it mostly borders Friulian, but also Bavarian to the north. It belongs to the Littoral dialect group, although it shows fewer similarities with other Littoral dialects, as it evolved from the Carinthian dialect base (15th century northern Slovene), as opposed to other Littoral dialects, which evolved either from western or southern Slovene. It is spoken by fewer than a thousand people and is listed as a definitely endangered language according to UNESCO's Atlas of the World's Languages in Danger. Despite this, Resians value their language and it is being passed down to younger generations.

The area where Resian is spoken is practically the same as the area of the Municipality of Resia (Italian: Comune di Resia). It is spoken entirely in northeastern Italy, in the Friuli-Venezia Giulia region in the province of Udine, making it the only Slovene dialect that is spoken exclusively in Italy. The speakers are settled in villages in the Resia Valley (Slovene: Rezija), along the Resia River (Rezija), as well as the upper Uccea Valley (Učja) on the Italian side. This includes several villages, including (from west to east): San Giorno (Bilä, Bela), Prato di Resia (Ravanca), Gniva (Njïwa, Njiva), Criacis (Krïžaca, Križeca), Oseacco (Osoanë, Osojane), Carnizza (Karnïca, Karnica), Stolvizza (Solbica), Coritis (Korïto, Korito), and Uccea (Učja). The Resia Valley is open to the west, where Friulian is spoken, and separated by tall mountains in other directions. There is a road connecting it to the Uccea Valley, reaching an elevation of more than 1,100 m above sea level, and it is further connected to the Torre and Soča Valleys, where Slovene is spoken. To the south, it is bordered by the Musi (Mužci) Mountains, to the east by Mount Canin (Ćanen, Kanin), and to the north by Mount Sard (Žard), therefore limiting possible connections with neighboring dialects and languages, which in turn has led to so many distinct features of Resian dialect.

The area was settled by Slovenes from the north, the area of today's Gail Valley dialect. Both areas remained connected until the 14th century, when sparsely populated Slovenes living in the Raccolana and Dogna Valleys started speaking Romance languages. There is no Slovene-speaking minority in that area today because it is mainly populated by Friulian and German speakers.

Standard Resian was developed by Han Steenwijk from the University of Padua and his colleagues Alfonso Barazzutti, Milko Matičetov, Pavle Merkù, Giovanni Rotta, and Willem Vermeer in the 1990s and continuing today. To date, they have standardized the writing, pronunciation, and declension. At first it was suggested to base the standard language on a central microdialect, particularly that of Gniva (Njïva, Njiva), but later it was decided to allow four forms of standard Resian, based on the four microdialects of four larger villages: San Giorno (Bila, Bela), Gniva (Njïva, Njiva), Oseacco (Osoanë, Osojane), and Stolvizza (Solbica). For other areas of grammar, only the microdialect of San Giorno can be used because it is the only one described in sufficient detail thanks to Steenwijk's extensive research.

Resian belongs to the western subgroup of the South Slavic branch of the Slavic languages, together with Slovene, which includes the Natisone Valley dialect, and Serbo-Croatian. It represents the far northwestern part of the dialect continuum. The closest written language is the Natisone Valley dialect and the closest standard language is Slovene. The closest (other) Slovene dialect is the Torre Valley dialect, another dialect known for little mutual intelligibility with other dialects. Written Resian can be understood by most Slovenes, partially also due to its similar orthography. Spoken Resian, however, is much more difficult to understand, with the main reason being centralization of vowels, making them more difficult to distinguish. Speakers of the Torre Valley and Natisone Valley dialects, as well as other dialects in Littoral dialect group, can understand spoken Resian most easily because they have the most shared features and they all have extensive vocabulary from Friulian and Italian.

Mutual intelligibility with other South Slavic languages is even more difficult, although Resian has undergone the *sěnȏ > *sě̀no accent shift, and so these words are now accented on the same syllable as in Serbo-Croatian, as opposed to most Slovene dialects.

There is disagreement between native speakers of the dialect and linguists regarding whether Resian should be considered a separate language or only a dialect of Slovene. Resians were isolated from other Slovenes from the 14th century onward, before standard Slovene was developed, and later they never had the chance to learn it because there were no Slovene schools in that area and none of the Italian schools taught Slovene, not even as a foreign language. Resians thus not only have a hard time understanding Slovene, but they also do not feel themselves part of the Slovene nation because they were left out, and they consider themselves an ethnic group separate from Slovenes. In 2004, 1,014 out of 1,285 (78.9%) inhabitants of Resia signed a petition declaring that they are not Slovenes. The dialect also has its own orthography, which existed and was actively used even before standardization. Resian is also used instead of standard Slovene on bilingual signs and in public announcements.