The Hammond organ or Hammond organ (also Hammond for short) is an electromechanical organ named after its inventor Laurens Hammond.

Originally intended as a replacement for the pipe organ, it became an instrument of jazz through its use as an entertainment instrument; It was initially used in gospel music as an inexpensive replacement for pipe organs in North American churches. From there the Hammond organ spread into rock, rhythm and blues, soul, funk, ska, reggae, fusion. However, the Hammond organ was unable to establish itself as a full replacement for pipe organs.

It was most popular in the 1960s and 1970s. But even today their distinctive sound or imitations of this sound are still widespread in popular music. Over the decades, the Hammond organ (particularly the B-3 model combined with a Leslie speaker system) became an established instrument.

What all instruments have in common is the structure with two manuals and a pedal. However, the range of the manuals and the pedal keyboard are different for the different models. The upper manual is called Swell and the lower manual is called Great. These names are borrowed from the pipe organ and mean Great and Swell.