The Boston Symphony Orchestra (BSO) is an American orchestra based in Boston, Massachusetts. It is the second-oldest of the five major American symphony orchestras commonly referred to as the "Big Five". Founded by Henry Lee Higginson in 1881, the BSO performs most of its concerts at Boston's Symphony Hall and in the summer performs at Tanglewood.

Since its founding, the orchestra has had 17 music directors, including George Henschel, Serge Koussevitzky, Henri Rabaud, Erich Leinsdorf, William Steinberg and James Levine. Andris Nelsons is the current music director of the BSO. Seiji Ozawa has the title of BSO music director laureate. Bernard Haitink has held the title of conductor emeritus of the BSO. The orchestra has made gramophone recordings since 1917 and has occasionally played on soundtrack recordings for films including Schindler's List.