A string orchestra is an orchestra consisting solely of a string section made up of the bowed strings used in Western Classical music. 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 usually, but not always, the double bass.

The string section is composed of bowed instruments belonging to the violin family. It normally consists of first and second violins, violas, cellos, and double basses. It is the most numerous group in the standard orchestra. In discussions of the instrumentation of a musical work, the phrase "the strings" or "and strings" is used to indicate a string section as just defined. An orchestra consisting solely of a string section is called a string orchestra. Smaller string sections are sometimes used in jazz, pop, and rock music and in the pit orchestras of musical theatre.