Podlachian language (pudlaśka mova) is an East Slavic literary microlanguage based on the East Slavic dialects spoken by inhabitants of the southern part of Podlachian Voivodeship (Polish: województwo podlaskie) in Poland between the Narew (north) and Bug (south) rivers. The native speakers of these dialects usually refer to them by the adverbial term po-svojomu (in our own language). The unequivocal academic classification of the po-svojomu dialects has been disputed for many years among linguists as well as activists of ethnic minorities in Podlachia (Polish: Podlasie), who classify them as either Belarusian dialects with Ukrainian traits or Ukrainian dialects.

The East Slavic dialects of Podlachia between the Narew and Bug rivers are perceived differently by their native speakers. According to an estimate made by Jan Maksymiuk, the author of a Podlachian language standardization project, on the basis of the 2002 census in Poland, some 32,000 people in Podlachia, who declared Belarusian ethnicity, identified these dialects as Belarusian ones. At the same time, about 1.5 thousand speakers opting for Ukrainian ethnic origin described the same dialects as Ukrainian. Jan Maksymiuk, who was born in Podlachia and identifies himself as an ethnic Belarusian, considers them a dialectal periphery of the Ukrainian language. He also claims that the Podlachian language standard proposed by him is “lexically, phonologically and morphologically more distant from the Ukrainian literary standard than, for example, the Lemko language in Poland or the Rusyn language in Slovakia”.

The term Podlachian language (pudlaśka mova) as the name for a standardized written language based on the East Slavic dialects between the Narew and Bug rivers was used for the first time by Jan Maksymiuk in the April 2005 issue of the monthly magazine Czasopis. Earlier, in the February issue of Czasopis Jan Maksymiuk announced that he would use a modified Latin alphabet for his Podlachian writing system. He was inspired to begin his orthographic project by the 1977 doctoral dissertation The vocabulary of the village of Kuraszewo near Hajnówka written by philologist Jan Pietruczuk under the supervision of well-known Polish Slavist Michał Łesiów.

The dialects taken as the basis for developing the standardized orthography and grammar of Podlachian are located in three counties (Polish: powiat) of Podlaskie Voivodeship: Bielsk County, Hajnówka County and Siemiatycze County. The rural communes (Polish: gmina) in which, according to the 2002 census, Belarusians constituted a majority or a significant percentage of their inhabitants include: Czyże (88.8%), Dubicze Cerkiewne (81.3%), Orla (68.9%), Hajnówka (64.9%), Narew (49.2%), Narewka (47.3%), Bielsk Podlaski (46.7%), Kleszczele (41.8%), Czeremcha (28.7%), Nurzec-Stacja (16.4%), Milejczyce (13.1%), Białowieża (11.5%). In the three district cities the percentage of Belarusians declared in 2002 was as follows: Hajnówka (26.4%), Bielsk Podlaski (20.7%), Siemiatycze (1.5%).

The written standard of Podlachian is based on East Slavic dialects in the communes of Narew, Czyże, Bielsk, Hajnówka (northern part), Boćki, Siemiatycze, Milejczyce (western part), Nurzec-Stacja (western part), which are characterized by the palatalization of dental consonants before the etymological [i] and the occurrence of three diphthongs: [^uo], [^ɨe], [ⁱe]. This means that the standardized written system is based on the speech varieties with pronunciations like [xod^jit^ji], [z^jima], [s^jiɫa], [k^uon^j], [r^ɨeʒe], [s^jiem]. In the communes of Orla, Dubicze Cerkiewne, Kleszczele and Czeremcha the prevalent pronunciations are [xodɨtɨ], [zɨma], [sɨɫa], [k^jin^j], [r^jiʒe], [s^jim] and they were left outside the Podlachian standardization project by Jan Maksymiuk.

Following the road cleared by Jan Pietruczuk, Jan Maksymiuk identified 39 phonemes in Podlachian: 8 vowels and 31 consonants. Among the vowel phonemes there are two diphthongs (one of them has two allophones).

The Podlachian alphabet developed by Jan Maksymiuk is modelled on the so-called Belarusian Latin alphabet (Belarusian: беларуская лацінка): a Latin orthographic system that has been used sporadically for the past hundred years to spell the Belarusian language. The author of the Podlachian written standard added four graphemes to render in writing the specific Podlachian sounds that do not appear in Belarusian: ê, ô, ď, ť.

The correspondence between the Podlachian phonemes and graphemes is as follows: [i] – i, [ɨ] – y, [u] – u, [ⁱe] – iê, [^ɨe] – ê, [^uo] – ô, [e] – e, [o] – o; [a] – a; [p] – p, [b] – b, [f] – f, [v] – v, [m] – m, [n] – n, [n^j] – ń, [t] – t, [d] – d, [t^j] – ť, [d^j] – ď, [dz] – dz, [dz^j] – dź, [ts] – c, [ts^j] – ć, [s] – s, [s^j] – ś, [z] – z, [z^j] – ź, [l] – l, [ɫ] – ł, [ʃ] – š, [ʒ] – ž, [tʃ] – č, [dʒ] – dž, [r] – r, [j] – j, [k] – k, [ɡ] – g, [x] – ch, [ɣ] – h.