Jascha Heifetz (; February 2  [O.S. January 20] 1901 – December 10, 1987) was a Russian-American violinist. Many consider him the greatest violinist of all time. Born in Vilna (Vilnius), he moved as a teenager to the United States, where his Carnegie Hall debut was rapturously received. He was a virtuoso since childhood—Fritz Kreisler, another leading violinist of the twentieth century, said on hearing Heifetz's debut, "We might as well take our fiddles and break them across our knees."

He had a long and successful performing career. However, after an injury to his right (bowing) arm, he switched his focus to teaching.

Late in life, Heifetz became a dedicated teacher and a champion of socio-political causes. He publicly advocated to establish 911 as an emergency phone number, and crusaded for clean air. He and his students at the University of Southern California protested smog by wearing gas masks, and in 1967 he converted his Renault passenger car into an electric vehicle.