The violoncello, abbreviated as cello (/ˈɛl/ CHEL-oh; plural cellos or celli), is a bowed string instrument with four strings tuned in perfect fifths. It is a member of the violin family of musical instruments, which also includes the violin, and viola.

The cello is used as a solo musical instrument, as well as in chamber music ensembles, string orchestras, and as a member of the string section of symphony orchestras. It is the second-largest bowed string instrument in the modern symphony orchestra, the double bass being the largest.

Cellos were derived from other mid- to large-sized bowed instruments in the 16th century, such as the viola da gamba, and the generally smaller and squarer viola da braccio, and such instruments made by members of the Amati family of luthiers. The invention of wire-wrapped strings in Bologna gave the cello greater versatility. By the 18th century, the cello had largely replaced other mid-sized bowed instruments.[citation needed]