Silesian or Upper Silesian (Silesian: Ślůnsko godka, Czech: slezský jazyk, Polish: język śląski) is considered either a dialect of the Polish language (apart from the Lach dialects, which are usually regarded as a branch of the Czech language), or a separate Slavic language.

Silesian speakers currently live in the region of Upper Silesia, which is split between southwestern Poland and the northeastern Czech Republic. At present Silesian is commonly spoken in the area between historical border of Silesia on the east and a line from Syców to Prudnik on the west as well as in the Rawicz area. Until 1945 Silesian was also spoken in enclaves in Lower Silesia, as Lower Silesian, a German dialect, was spoken by the ethnic German majority population of that region at the time.

According to the last official census in Poland (2002), above 56,000 people declared Silesian as their native language, and over 173,000 people declared Silesian nationality (mainly in the Silesian Voivodeship). There are also about 100,000 Silesian (Cieszyn Silesian) speakers living in the Czech Republic; Cieszyn Silesian is also commonly spoken in the Polish part of Cieszyn Silesia. Speakers of Cieszyn Silesian dialect usually identify themselves on the nationality level as Poles. According to the last official census in Czech Republic, 10,878 Czechs declared Silesian nationality.^{[citation needed]}