A multi-instrumentalist is a musician who plays a number of different instruments.

Music written for symphony orchestra usually calls for a percussion section featuring a number of musicians who might each play a variety of different instruments during a performance. Orchestras will also often, but not always, call for several members of the woodwind section to be multi-instrumentalists. This is sometimes referred to as doubling. Typically, for example, one flute player in the orchestra will switch to playing the piccolo or alto flute when called to by the score. Similarly, clarinet players may double on bass clarinet, oboe players on cor anglais, and bassoon players on contrabassoon. Trumpet players may switch to piccolo trumpet for certain Baroque literature, and first trombone players may switch to alto trombone. Doubling elsewhere in the orchestra is rare.

The European Piffari, Stadtpfeifer and Waits were multi-instrumentalists, who played trumpet, sackbut, shawm, cornett, recorder and string-instruments. Musicians with an education of a Stadtpfeifer were Gottfried Reiche,Johann Joachim Quantz, Johann Christof Pezel and Sigmund Theophil Staden. Also many European church musicians of the 17th and 18th centuries were multi-instrumentalists, who played several instruments. Georg Philipp Telemann for example played violin, viola da gamba, recorder, flauto traverso, oboe, shawm, sackbut and double bass. A contemporary multi-instrumentalist is the German kantor Helmut Kickton who performs church music on organ, violin, viola, cello, double bass, recorder, euphonium, guitar and kettledrums. More recently, German violinst Julia Fischer has also been credited with and acclaimed for being an excellent pianist as well, which is demonstrated in her late recordings of several renowned classical piano pieces.