A tremulant (from Latin: tremulus, "trembling"; French: tremblant, Italian: tremolo, Spanish: temblor) is a device on a pipe organ which varies the wind supply to the pipes of one or more divisions (or, in some cases, the whole organ). This causes their amplitude and pitch to fluctuate, producing a tremolo and vibrato effect. A large organ may have several tremulants, affecting different ranks (sets) of pipes. Many tremulants are variable, allowing for the speed and depth of tremolo to be controlled by the organist. The tremulant has been a part of organ building for many centuries, dating back to Italian organs of the sixteenth century.

The tremulant should not be confused with the celeste, which consists of two distinct ranks of pipes, one tuned slightly sharp or flat from the other, producing an undulating effect when they are used together.