Born in Budapest in 1888, he studied piano with his mother and, at the age of 15, entered the Franz Liszt Academy -- an institution that also boasts Bela Bartók, Zoltan Kodály, Ernst von Dohnányi, George Szell, Eugene Ormandy, Georg Solti and Antal Dorati as graduates. Reiner gained conducting experience at a number of regional opera houses before eventually returning to Budapest in 1911 to serve at the city's Volksoper, where his reputation as a conductor of special abilities finally emerged.

In 1914 Reiner accepted a position at the Dresden Court Opera, where he formed a fortuitous relationship with both the conductor Arthur Nikisch and the composer Richard Strauss; Reiner would eventually give the German premier of Strauss' Die Frau ohne Schatten, and would remain a devoted interpreter of the composer's works throughout his career. The economic chaos and emergent anti-Semitism that followed the First World War made Reiner anxious to leave Europe, and an invitation (in 1921) to become the music director of the Cincinnati Symphony Orchestra provided just the right opportunity. From that point onward, Reiner's career was firmly rooted in the United States, where he became a citizen in 1928.

After resigning his post at Cincinnati Reiner became a professor of conducting at the Curtis Institute of Music in Philadelphia, where his students included both the young Leonard Bernstein and Lukas Foss; Bernstein, in particular, credited Reiner with a great deal of influence in his development.

In 1938 he became the director of the Pittsburgh Symphony -- one of several positions that established Reiner as a fine builder of orchestras, with a talent for steering ensembles toward new levels of quality and success. A number of Reiner's well-known recordings stem from his tenure there. Guest appearances during his Pittsburgh years include those at Covent Garden and the San Francisco Symphony. From Pittsburgh he moved to the Metropolitan opera, where he remained on the conductor roster until 1953; his advocacy of Strauss' operas was especially strong there, and his performances of Salome and Elektra number among the most memorable evenings in the Met's history.

1953 was a watershed year for Reiner, since it was then that he assumed the directorship of the Chicago Symphony Orchestra. This was to become his signature partnership, and the position that would establish his lasting legacy. His relationship with the orchestra was never a smooth one -- he was known for hostility and impatience in rehearsal, and for firing musicians for mistakes in concerts -- but he undeniably raised the ensemble from its status as a good American orchestra to that of one of the finest in the world. Unlike a number of other prominent conductors who excelled in narrow corners of the musical canon, Reiner maintained his excellent standards and clarifying precision throughout an especially broad repertory that crossed boundaries of nationality and style. He was as renowned for his performances of new works, such as Bartók's Concerto for Orchestra -- a piece that Reiner himself commissioned from the dying composer -- and Alan Hovhaness' Mysterious Mountain as he was for his Mahler, Strauss and Haydn. His tenure in Chicago also resulted in what was then an unprecedented volume of fine recordings, some of which still remain as favorites, despite the improved fidelity of modern competitors. Reiner resigned from Chicago in 1962 (after only nine seasons), and died the following year of heart failure.