A fret is a space between two fretbars on the neck of a stringed instrument. Frets usually extend across the full width of the neck. On most modern western fretted instruments, frets are the spaces between the metal strips (fretbars) that are inserted into the fingerboard. On some historical instruments and non-European instruments, frets are made of pieces of string tied around the neck.

The neck of a guitar showing the nut (in the background, coloured white) and first four frets

Frets divide the neck into fixed segments at intervals related to a musical framework. On instruments such as guitars, each fret represents one semitone in the standard western system, in which one octave is divided into twelve semitones. Fret is often used as a verb, meaning simply "to press down the string behind a fret". Fretting often refers to the frets and/or their system of placement.