Wymysorys (Wymysiöeryś, pronounced [vɨmɨˈsʲøːrɪɕ, vɨmɨˈɕœ̯ɛrɪɕ]), also known as Vilamovian, Wilamowicean, or Wilmesaurisch, is a West Germanic language spoken by the Vilamovian ethnic minority in the town of Wilamowice, Silesian Voivodeship, Poland (Wymysoü in Wymysorys), on the border between Silesia and Lesser Poland, near Bielsko-Biała. It is considered an endangered language, possibly the most so of any of the Germanic languages. There are probably fewer than 20 native users of Wymysorys, virtually all bilingual; the majority are elderly.

The status of Wymysorys is complex because, genealogically, it belongs to the East Central dialect group of High German. Nevertheless, based on the self-identification of its users as a group separate from the Germans and the existence of a literary language, it can be considered a separate language.^{[citation needed]}

It belongs to the dialect group of the former Bielsko-Biała language island [pl; de], which includes the Alzenau dialect.

In origin, Wymysorys is considered to derive from 12th-century Middle High German, with a strong influence from Polish, and presumably also some influence from Low German, Dutch, Old English and perhaps Frisian. The inhabitants of Wilamowice are thought to be descendants of German, Flemish and Scottish settlers who arrived in Poland during the 13th century. Many of the inhabitants claim that they are descended from the people of Flanders, Friesland, and Holland, with others claiming to be descended from the Anglo-Saxons. Although historically derived from the German dialect continuum, Wymysorys is not mutually intelligible with Standard German. Unlike in other West Germanic enclave communities in Polish-speaking territory, where closely related dialects (e.g. Halcnovian) were spoken, Wymysorys speakers did not self-identify as Germans and used Polish, not German, as Dachsprache.

Wymysorys was the vernacular language of Wilamowice until World War II. However, it seems it has been in decline since the late 19th century. In 1880 as many as 92% of the town's inhabitants spoke Wymysorys (1,525 out of 1,662 people), in 1890 – only 72%, in 1900 – 67%, in 1910 – 73% again. Although Wymysorys was taught in local schools (under the name of "local variety of German"), since 1875 the basic language of instruction in most schools in Austro-Hungarian Galicia was Polish. During World War II and the German occupation of Poland, Wymysorys was openly promoted by the Nazi administration, but after the war the tables turned: local communist authorities forbade the use of Wymysorys in any form. The widespread bilingualism of the people saved most local residents from being forcibly resettled to Germany, but many of them stopped teaching their children their language or even using it in daily life. Although the ban was lifted after 1956, Wymysorys has been gradually replaced by Polish, especially among the younger generation. Most of the inhabitants have the same surnames (Mozler, Rozner, Figwer, Biba, Foks, Sznajder), which led to the use of nicknames (Fliöer-Fliöer, Hȧla-Mockja, i.e. Florian, son of Florian or Maciej, son of Elżbieta).

Nowadays, as part of saving the Wymysorys culture, new songs and lyrics are written in this language. The play Hobbit. Hejn ȧn cyryk was written in Wymysorys, based on the prose of J. R. R. Tolkien, and was staged, among others, at the Polish Theatre in Warsaw in February 2016.

Acting on a proposal by Tymoteusz Król, the Library of Congress added the Wymysorys language to the register of languages on 18 July 2007. It was also registered in the International Organization for Standardization, where it received the wym ISO 639-3 code. In a 2009 UNESCO report Wymysorys has been reported as "severely endangered" and nearly extinct.

Members of the Wikimedia Polska association were also involved in saving this dying language. As part of the "Wilamowice" project, Wymysorys words read by Józef Gara were recorded, and the Wymysorys dictionary in Wiktionary was supplemented (in 2018, the dictionary consisted of over 7,000 words).