Plautdietsch (pronounced [ˈplaʊt.ditʃ]) or Mennonite Low German is a Low Prussian dialect of East Low German with Dutch influence that developed in the 16th and 17th centuries in the Vistula delta area of Royal Prussia. The word Plautdietsch translates to "flat (or low) German" (referring to the plains of northern Germany or the simplicity of the language). In other Low German dialects, the word for Low German is usually realised as Plattdütsch/Plattdüütsch [ˈplatdyːtʃ] or Plattdüütsk [ˈplatdyːtsk], – very often also as Plattdeutsch – but the spelling Plautdietsch is used to refer specifically to the Vistula variant of the language.
Plautdietsch was a Low German dialect like others until it was taken by Mennonite settlers to the southwest of the Russian Empire starting in 1789. From there it evolved and subsequent waves of migration brought it to North America, starting in 1873.