Swiss German (Standard German: Schweizerdeutsch, Alemannic German: Schwiizerdütsch, Schwyzerdütsch, Schwiizertüütsch, Schwizertitsch Mundart, and others; Romansh: tudestg svizzer) is any of the Alemannic dialects spoken in the German-speaking part of Switzerland, and in some Alpine communities in Northern Italy bordering Switzerland. Occasionally, the Alemannic dialects spoken in other countries are grouped together with Swiss German as well, especially the dialects of Liechtenstein and Austrian Vorarlberg, which are closely associated to Switzerland's.

Linguistically, Alemannic is divided into Low, High and Highest Alemannic, varieties all of which are spoken both inside and outside Switzerland. The only exception within German-speaking Switzerland is the municipality of Samnaun, where a Bavarian dialect is spoken. The reason Swiss German dialects constitute a special group is their almost unrestricted use as a spoken language in practically all situations of daily life, whereas the use of the Alemannic dialects in other countries is restricted or even endangered.

The dialects that comprise Swiss German must not be confused with Swiss Standard German, the variety of Standard German used in Switzerland. Swiss Standard German is fully intelligible to all speakers of Standard German, and is one of three major standards of German today. While Swiss Standard German is internationally easily intelligible, many people in Germany – especially in the north – do not understand non-standard Swiss German. An interview with a Swiss German speaker, when shown on television in Germany, generally requires subtitles. Although Swiss German is the native language in the German-speaking part of Switzerland, Swiss school students are taught Swiss Standard German from the age of six. They are thus capable of understanding, writing and speaking Standard German, with varying abilities.

Unlike most regional languages in modern Europe, Swiss German is the everyday spoken language for the majority of the population, in all social strata, from urban centers to the countryside. Using Swiss German conveys neither social nor educational inferiority and is done with pride. There are a few settings where speaking Standard German is demanded or polite, e.g., in education (but not during breaks in school lessons, where the teachers will speak with students in Swiss German), in multilingual parliaments (the federal parliaments and a few cantonal and municipal ones), in the main news broadcast or in the presence of non-Alemannic speakers. This situation has been called a "medial diglossia", since the spoken language is mainly Swiss German, whereas the written language is mainly (the Swiss variety of) Standard German.

In 2014, about 87% of the people living in the German-speaking portion of Switzerland were using Swiss German in their everyday lives.

Swiss German is intelligible to speakers of other Alemannic dialects, but largely unintelligible to speakers of Standard German who lack adequate prior exposure. This is also a challenge for French- or Italian-speaking Swiss who learn Standard German at school. In the rare cases that Swiss German is heard on TV in Germany and Austria, the speaker is most likely to be dubbed or subtitled. More commonly, a Swiss speaker will speak Standard German on non-Swiss media.

"Dialect rock" is a music genre using the language; many Swiss rock bands, however, sing in English instead.

The Swiss Amish of Adams County, Indiana, and their daughter settlements also use a form of Swiss German.