Silesians (Silesian: Ślōnzŏki or Ślůnzoki; Silesian German: Schläsinger or Schläsier; German: Schlesier pronounced [ˈʃleːzi̯ɐ] ^ⓘ; Polish: Ślązacy; Czech: Slezané) is both a linguistic as well as a geographical term for the inhabitants of Silesia, a historical region in Central Europe divided by the current national boundaries of Poland, Germany, and Czechia. Historically, the region of Silesia (Lower and Upper) has been inhabited by Polish (West Slavic Lechitic people), Czechs, and Germans. Therefore, the term Silesian can refer to anyone of these ethnic groups. However, in 1945, great demographic changes occurred in the region as a result of the Potsdam Agreement leaving most of the region ethnically Polish and/or Slavic Upper Silesian. The names of Silesia in different languages most likely share their etymology—Polish: Śląsk^ⓘ; German: Schlesien pronounced [ˈʃleːzi̯ən] ^ⓘ; Czech: Slezsko [ˈslɛsko]; Lower Silesian: Schläsing; Silesian: Ślōnsk [ɕlonsk]; Lower Sorbian: Šlazyńska [ˈʃlazɨnʲska]; Upper Sorbian: Šleska [ˈʃlɛska]; Latin, Spanish and English: Silesia; French: Silésie; Dutch: Silezië; Italian: Slesia; Slovak: Sliezsko; Kashubian: Sląsk. The names all relate to the name of a river (now Ślęza) and mountain (Mount Ślęża) in mid-southern Silesia, which served as a place of cult for pagans before Christianization.

Ślęża is listed as one of the numerous Pre-Indo-European topographic names in the region (see old European hydronymy). According to some Polonists, the name Ślęża [ˈɕlɛ̃ʐa] or Ślęż [ɕlɛ̃ʂ] is directly related to the Old Polish words ślęg [ɕlɛŋk] or śląg [ɕlɔŋk], which means dampness, moisture, or humidity. They disagree with the hypothesis of an origin for the name Śląsk [ɕlɔ̃sk] from the name of the Silings tribe, an etymology preferred by some German authors.

The term "Silesia" is a Latinized word of the original Polish/Lechitic name "Śląsk" inhabited by the ancient Lechitic tribes called Ślężanie. In Silesia, there are many places of the ancient Slavic Lechitic pagan cult of these ancient people, for example Góra Ślęża.^{[citation needed]}

About 209,000 of the Upper Silesian population declared themselves as pure Silesians, 376,000 people declared themselves as having a joint Silesian and Polish nationality while only 471,000 people declared themselves to be of only Polish nationality from Silesia in the 2011 Polish national census making them the largest minority group in Poland. About 126,000 people declared themselves as members of the German minority (58,000 declared it jointly with Polish nationality), making it the third largest minority group in the country (93% of Germans living in Poland are in the Polish parts of Silesia). 31,301 people declared Silesian nationality in the 2021 Czech census, including 18,850 of those who declared two nationalities (44,446 in Czechoslovakia in 1991), and 6,361 people declared joint Silesian and Moravian nationality in the 1991 Slovak national census. Over 85% of the population in the Polish part of Upper Silesia declare themselves as Poles, and in the Czech part as Czechs.

During the German occupation of Poland, Nazi authorities conducted a census in East Upper Silesia in 1940. At the time, 157,057 people declared Silesian nationality (Slonzaken Volk), and the Silesian language was declared by 288,445 people. However, the Silesian nationality could only be declared in the Cieszyn part of the region. Approximately 400–500,000 respondents from the other areas of East Upper Silesia who declared "Upper Silesian nationality" (Oberschlesier) were assigned to the German nationality category. After World War II in Poland, the 1945 census showed a sizable group of people in Upper Silesia who declared Silesian nationality. According to police reports, 22% of people in Zabrze considered themselves to be Silesians, and that number was around 50% in Strzelce County.

Archaeological findings of the 20th century in Silesia confirm the existence of an early settlement inhabited by Celtic tribes.

Until the 2nd century some parts of Silesia were populated by Celtic Boii, predecessors of the states of Bohemia and Bavaria and subsequently until the 5th century, by the Germanic Silingi, a tribe of the Vandals, which moved south and west to invade Andalusia. Silesia remained depopulated until the second phase of the migration period.^{[citation needed]}

The Slavs, predominantly White Croats entered the depopulated territory of Silesia in the first half of the 6th century. The Slavic territories were mostly abandoned, because the Celtic and Germanic tribes that lived there before had moved west. Chronologically, the first group of Slavs were those that dwelt by the Dnieper River, the second was the Sukov-Dzidzice type Slavs, and the last were groups of Avaro-Slavic peoples from the Danube river areas. In the early 9th century, the settlement stabilized. Local West Slavs began to erect a series of defensive systems, such as the Silesian Przesieka and the Silesia Walls to guard them from invaders. The north-eastern border with Western Polans was not reinforced, due to their common culture and language.