German dialect is dominated by the geographical spread of the High German consonant shift, and the dialect continuum that connects the German with the Dutch language.

In German linguistics, German dialects are distinguished from varieties of standard German.

The variation among the German dialects is considerable, with only the neighbouring dialects being mutually intelligible. Low German, most Upper German and High Franconian dialects, and even some Central German dialects when spoken in their purest form, are not intelligible to people who only know standard German. However, all German dialects belong to the dialect continuum of High German and Low German. In the past (roughly till the end of the Second World War) there was a dialect continuum of all the continental West Germanic languages because nearly any pair of neighbouring dialects were perfectly mutually intelligible.

The German dialect continuum is typically divided into High German and Low German. The terms derive from the geographic characteristics of the terrain where they are spoken rather than from social status accorded to them.

Pennsylvania Dutch refers to immigrants and their descendants from southwestern Germany and Switzerland who settled in Pennsylvania in the 17th and 18th centuries. Historically they have spoken the dialect of German known as Pennsylvania Dutch or Pennsylvania German.

The first major emigration of Germans to America resulted in the founding of the Borough of Germantown in northwest Philadelphia County, Pennsylvania on October 6, 1683. Mass emigration of Palatines began out of Germany in the early 18th century.

The Pennsylvania Dutch maintained numerous religious affiliations, with the greatest number being Lutheran or Reformed, but many Anabaptists as well. The Anabaptist religions promoted a simple lifestyle and their adherents were known as Plain people or Plain Dutch, as opposed to the Fancy Dutch who tended to assimilate more easily into the American mainstream.

Over time, the various dialects spoken by these immigrants fused into a unique dialect known as Pennsylvania Dutch or Pennsylvania German. At one time, over a third of Pennsylvania's population spoke this language, which also had an impact on the local dialect of English.