Silesian, occasionally called Upper Silesian, is an ethnolect of the Lechitic group spoken in Upper Silesia. While having secured some international recognition as a language, there is a debate on whether Silesian is either a dialect of Polish or a distinct language, and if Silesians are either a regional ethnic group within the Polish nation or a distinct ethnic minority that historically emerged, but later diverged from, the Polish people. Some Silesians identify as a regional ethnic group within the Polish nation, while others view themselves as a distinct ethnic minority. Its vocabulary was significantly influenced by Central German due to the existence of numerous Silesian German speakers in the area prior to World War II and after. The first mentions of Silesian as a distinct lect date back to the 16th century, and the first literature with Silesian characteristics to the 17th century.
Linguistic distinctiveness of Silesian has long been a topic of discussion among Poland's linguists, especially after all of Upper Silesia was included within the Polish borders following World War II. Some regard it as one of the four major dialects of Polish, while others classify it as a separate regional language, distinct from Polish. The dispute over the status of Silesian is considered to be of purely political character. According to the official data from the 2021 Polish census, 467 145 people use Silesian on daily basis. Internationally, Silesian has been fully recognized as a language since 2007, when it was accorded the ISO 639-3 registration code szl.