A humbucker, humbucking pickup, or double coil, is a guitar pickup that uses two wire coils to cancel out noisy interference from coil pickups. Humbucking coils are also used in dynamic microphones to cancel electromagnetic hum. Humbuckers are one of two main types of guitar pickups. The other is called a single coil.

The humbucking coil was invented in 1934 by Electro-Voice, an American professional audio company based in South Bend, Indiana, that Al Kahn and Lou Burroughs incorporated in 1930 for the purpose of manufacturing portable public address equipment, including microphones and loudspeakers. A twin coiled guitar pickup invented by Arnold Lesti in 1935 is arranged as a humbucker, and the patent USRE20070 describes the noise cancellation and current summation principles of such a design. This "Electric Translating Device" employed the solenoid windings of the pickup to magnetize the steel strings by means of switching on a short D.C. charge before switching over to amplification. In 1938, A. F. Knoblaugh invented a pickup for stringed instruments involving two stacked coils described in U.S. patent 2,119,584. This pickup was to be used in pianos, since he was working for Baldwin Piano at the time. The April 1939 edition of Radio Craft magazine shows how to construct a guitar pickup made with two identical coils wrapped around self-magnetized iron cores, where one is then flipped over to create a reverse-wound, reverse-polarity, humbucking orientation. The iron cores of these pickups were magnetized to have their north–south poles at the opposite ends of the core, rather than the now more common top-bottom orientation.

To overcome the hum problem for electric guitars, a new humbucking pickup was designed by Seth Lover of Gibson in 1955 under the instruction of then-president Ted McCarty. Because of its use of a "Patent Applied For" sticker on the underside of the pickup, it became popularly known as the P.A.F. and would be widely be used in Gibson's guitars, starting with the Les Paul. At the same time Lover was working on his humbucker, Ray Butts developed a similar pickup on his own, the Filter'Tron, which was taken up by Gretsch guitars. Although Gibson's patent was filed almost two years before Gretsch's, their patent was issued four weeks after Gretsch's. Both patents describe a reverse-wound and reverse-polarity pair of coils. Rickenbacker too had developed dual-coil pickups arranged in a humbucking pattern but dropped the design in 1954 due to the perceived distorted sound.^{[citation needed]}

In 1972, DiMarzio pioneered the aftermarket replacement guitar pickup with their "Super Distortion" humbucker, which was designed to fit Gibson-style pickup mounts and featured greatly-increased output compared to stock humbuckers installed in guitars of the time. For this reason, it became a favorite of many hard rock guitarists. Many manufacturers, such as Seymour Duncan and EMG, followed suit, offering aftermarket pickups that included many new humbucker designs.

Variants of other brands have been equipped with humbuckers, even types which are traditionally associated with single-coil pickups, like Fender Stratocasters and Telecasters. In particular, the replacement of the bridge pickup in a Stratocaster-type guitar with a humbucker, resulting in a pickup configuration noted as H-S-S (starting at bridge pickup: H for humbucker, S for single coil) has gained much popularity. Guitars in this configuration are sometimes referred to as "Fat Strats", because of the fatter, rounder tone offered by the humbucking pickup, and are also closely related to the "Superstrat" style of guitar.

In any magnetic pickup, a vibrating guitar string, magnetized by a fixed magnet within the pickup, induces an alternating voltage across its coil. However, wire coils also make excellent antennas and are therefore sensitive to electromagnetic interference caused by alternating magnetic fields from mains wiring (mains hum) and electrical appliances like transformers, motors, and computer screens, especially older CRT monitors. Guitar pickups reproduce this noise, which can be quite audible, sounding like a constant hum or buzz. This is most noticeable when using distortion, fuzz, compressors, or other effects which, by adding gain to low-level signals, reduce the signal-to-noise ratio and therefore amplify the unwanted interference relative to the signal from the strings.

Humbuckers work by pairing a coil that has the north poles of its magnets oriented up (toward the strings) with another coil alongside it with the south pole of its magnets oriented up. By connecting the coils together out of phase, the interference is significantly reduced via phase cancellation: the string signals from both coils add up instead of canceling because the magnets are placed in opposite polarity. This dramatically improves the signal-to-noise ratio. The technique has something in common with what electrical engineers call common-mode rejection, and is also found in the balanced lines used in audio equipment. By convention, both humbucker coils are wound counterclockwise. The coils can be connected in series or in parallel in order to achieve this hum-cancellation effect, but humbucker pickups tend to be connected in series because that doubles the signal of the strings while keeping the hum reduced. Some types of humbucker pickups can be manually split (with a switch or within the pickup selector) so that only one coil is active.

Slightly smaller than a traditional humbucker/double coil form factor.