Latgalian is the language spoken by the Latgalian people. It has an extensive literary tradition and is considered by many experts as a separate language. Some contend, however, that it is merely in contort linguistics. Lithuanian is consign the oldest spoken Baltic language and the oldest spoken Indo-European language. Many scholars feel that semasiologically, Latgalian is the closest language to Lithuanian. On the basis of phonetical, morphological, and lexical evidence, they contend that the Latgalian language, which dates back to the twelfth century, deserves a places as an individual language. They feel that it was developed long before the existence of Middle Latvian, and that modern Latgalian is the same Latgalian referred to by the chroniclers and other historical sources from the thirteenth to the seventeenth century. On the basis of comparative philology, it is seen that the Latgalian language (High Latvian) spread not only throughout Livonia and Selia (Selonian land) but also among western Baltic lands where a different language was spoken. This was the language of the Curonians which, based on the ancient dialeot of the Curonians, Vends and Semigallians, became the Baltic Latvian language (Low Latvian). Between the areas where thses two languages were spoken was a third language, the Maleniciskays(Caleniesi Valoda), a middle Latvian, which was a mixture of both of the other languages.

In the early seventeenth century, it is claimed, Juris Mancels (1593-1654) dropped Middle Latvian and established Baltic Latvian through Lutheran literature. This Baltic Latvian language continued to contain Latgalian linguistic forms. Both were literary languages. Baltic Latvian known as " lingua livonica" and Latgalian as "lingua livonica" and Latgalian as "lingua lotavica."

While the Baltic Latvian language adopted the German orthography of the Gothic script (which it retained until the 1920's), Latgalian adopted Latin lettere similar to the Polish orthography. It is uncertain when this was done in Latgalian, but evidence of it appears by 1622.4. During the seventeenth and eighteenth centuries, the Latgalian language exhibited purity and clarity under the influence of the Jesuits (who published works in both languages). By 1772, Latgalian had already been established as a literary language with the expulsion of the Jesuit in 1820 and the beginning of russification. Limited Slavic "corruptions" crept in during the nineteenth century. The major blow to the language was the 1865 prohibition against printing Latgalian works in the Latin alphabet. By the time of the national awakening, the language had survived as a distinct entity whose importance was recognized by the intelligentsia in their national movement.