The term Prussian Lithuanians or Lietuvininkai (singular: Lietuvininkas, also Lietuvininkai) refers to a Western Lithuanian ethnic group, which did not form a nation and inhabited a territory in East Prussia called Prussian Lithuania or Lithuania Minor (Lithuanian: Prūsų Lietuva, Mažoji Lietuva, German: Preußisch-Litauen, Kleinlitauen) in contrast to the Grand Duchy of Lithuania and later the Republic of Lithuania (Lithuania Major).
Unlike most Lithuanians, who remained Roman Catholic after the Protestant Reformation, most Lietuvininkai became Lutheran-Protestants (Evangelical-Lutheran).
There were 121,345 speakers of Lithuanian in the Prussian census of 1890. Almost all fled or were expelled after World War II, when East Prussia was divided between Poland and the Soviet Union. The northern part became the Kaliningrad Oblast, while the southern part was attached to Poland. Only the small Klaipėda Region (German: Memelland) was attached to Lithuania.