Boris Kroyt (3 June 1897 – 15 November 1969) was a classical violinist and violist. He was the violist of the Budapest String Quartet from 1936 until the ensemble disbanded in 1967. Kroyt was born to a Jewish-Ukrainian family in Odessa, but spent his early life and career in Germany where he had been a child prodigy violinist. From the outbreak of World War II until his death at the age of 72, he lived in the United States and had become a naturalized U.S. citizen in 1944.