Saterland Frisian, also known as Sater Frisian or Saterlandic (Seeltersk), is the last living dialect of the East Frisian language. It is closely related to the other Frisian languages—North Frisian, which, like Saterland Frisian, is spoken in Germany and West Frisian, which is spoken in the Netherlands.

Old East Frisian used to be spoken in East Frisia (Ostfriesland), the region between the Dutch river Lauwers and the river Weser, in the German state of Lower Saxony. The area also included two small districts on the east bank of the Weser, the lands of Wursten and Würden. The Old East Frisian language could be divided into two dialect groups: Weser Frisian to the east, and Ems Frisian to the west. From 1500 onwards Old East Frisian slowly had to give way to the severe pressure put on it by the surrounding Low German dialects, and nowadays it is all but extinct.

By the middle of the seventeenth century Ems Frisian had almost completely died out. Weser Frisian for the most part did not last much longer and held on only until 1700, although there are records of it still being spoken in the land of Wursten, to the east of the river Weser, in 1723. It held out the longest on the island of Wangerooge, where the very last Weser Frisian speaker was recorded as having died in 1953. Today, the Old East Frisian language is no longer spoken within the historical borders of East Frisia, yet a large number of the inhabitants of that region still consider themselves Frisians and refer to their dialect of Low German as Freesk. In this dialect, referred to as Ostfriesisch in German, the Frisian substratum is still evident, despite heavy germanisation.

Frisian language can refer to: