A fret is a raised portion on the neck of a stringed instrument, that extends generally across the full width of the neck. On most modern western instruments, frets are metal strips inserted into the fingerboard. On historical instruments and some non-European instruments, pieces of string tied around the neck serve as 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 where one octave is divided into twelve semitones.

"To 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.