Boris Thomashefsky, born Boruch-Aharon Thomashefsky, was a Ukrainian-born Jewish singer and actor who became one of the biggest stars in Yiddish theater.

Yiddish theatre consists of plays written and performed primarily by Jews in Yiddish, the language of the Central European Ashkenazi Jewish community. The range of Yiddish theatre is broad: operetta, musical comedy, and satiric or nostalgic revues; melodrama; naturalist drama; expressionist and modernist plays. At its height, its geographical scope was comparably broad: from the late 19th century until just before World War II, professional Yiddish theatre could be found throughout the heavily Jewish areas of Eastern and East Central Europe, but also in Berlin, London, Paris, Buenos Aires and New York City.