Fretless basses have a distinct sound - the absence of frets means that the string must be pressed down directly onto the wood of the fingerboard and can buzz against it as with the double bass. This allows players to use expressive devices such as glissando, vibrato and microtonal intonations (such as quarter tones and just intonation). Some bassists use both fretted and fretless basses in performances, according to the type of material they are performing.

It is rumoured that Bill Wyman made the first known fretless bass guitar in 1961 by converting an inexpensive Japanese fretted bass. This fretless bass can be heard on Rolling Stones songs such as Paint it Black.

The first production fretless bass was the Ampeg AUB-1 introduced in 1966. Fender introduced a fretless version of the Precision Bass in 1970. Fusion-jazz virtuoso Jaco Pastorius created his own fretless bass by pulling the frets out of a sunburst Fender Jazz Bass and coating the fretboard with epoxy.