A string orchestra is an orchestra consisting solely of a string section. The instruments of such an orchestra are most often the following: the violin, which is divided into first and second violin players, the viola, the cello, and the double bass. String orchestras can be of chamber orchestra size ranging from between 12 (4.3.2.2.1 = 12) and 21 musicians (6.5.4.4.2 = 21) sometimes performing without a conductor, or consist of the entire string section of a large symphony orchestra which could have 60 musicians (16.14.12.10.8 = 60; Gurre-Lieder calls for 84: 20.20.16.16.12).

Film scores generally have quite varied string set-ups: for example,James Newton Howard's score for The Last Airbender featured 33 violins, 21 violas, 14 celli and 15 double basses, making it a total of 83 strings.

A twentieth-century development has been the reappearance of the concerto grosso pitting of soloists against the full ensemble. During the past eras of pop music, it also employed up to 65-piece string orchestras