American symphony orchestra, based in Philadelphia, Pa. It was founded in 1900 under the direction of Fritz Sheel, who served until 1907. Subsequent conductors have been Carl Pohlig (1907–12), Leopold Stokowski (1912–36), Eugene Ormandy (Ormandy, Eugene) (1936–80; director laureate until 1985), Riccardo Muti (Muti, Riccardo) (1980–92), and Wolfgang Sawallisch (from 1993).

From Stokowski's tenure, the orchestra was renowned for its interpretation of the symphonic repertoire and for its interest in new music and musical technologies, as well as for its recordings, concert tours, and children's concert programming. Stokowski led the orchestra in world premieres of Rachmaninoff's Symphony No. 3 in A Minor and Fourth Piano Concerto and Schoenberg's Violin Concerto. In 1939 he and the orchestra performed on the soundtrack of Walt Disney's film Fantasia.

Under Ormandy, the Philadelphia Orchestra was known for its sonorous tone and its interpretation of the repertoire of French, German, and Russian music of the Postromantic and early modern eras. Ormandy conducted world premieres of Bartók's Third Piano Concerto and Webern's Three Pieces for Orchestra. Muti commissioned works by contemporary composers, including Shulamit Ran, and appointed the orchestra's first composer-in-residence, Bernard Rands. Muti also led concert performances of operas.

Since the 1930s the orchestra has given summer concerts, first at the Robin Hood Dell and, since 1976, at the Mann Music Center.