Fretless instruments have a smooth fingerboard without metal frets, allowing notes to be played by finger placement alone. This design enables continuous pitch variation, subtle slides, and expressive vibrato that are not possible on fretted instruments.

They are most commonly found on bass guitars but also exist in guitars and other stringed instruments. Fretless instruments are valued for their warm, vocal-like tone and expressive feel, making them popular in jazz, fusion, ambient, and experimental styles where nuance and articulation are important.