The cello (also violoncello or 'cello) is a stringed instrument, closely related to the violin. The cello is much larger than a violin, and unlike that instrument is played in an upright position between the legs of the seated musician, resting on a metal spike. The player draws their bow horizontally across the strings.

The cello plays notes on the bass clef, and has 4 strings tuned in fifths: C (the lowest), G, D and A (below middle C) - these are tuned exactly one octave below the viola. For the highest notes, the cello sometimes uses the tenor clef and occasionally the treble clef.

The name cello is an abbreviation of the Italian violoncello, which means 'little violone'. The violone is an obsolete instrument whose name literally means 'big viola'. It was similar to a modern double bass.