The Fender Jazz Bass (often shortened to "J-Bass") is the second model of electric bass guitar created by Leo Fender. It is distinct from the Precision Bass in that its tone is brighter and richer in the midrange and treble with less emphasis on the fundamental frequency. The body shape is also different from the Precision Bass, in that the Precision Bass has a symmetrical lower bout on the body, designed after the Telecaster and Stratocaster lines of guitars, while the Jazz Bass has an offset lower bout, mimicking the design aesthetic of the Jaguar and Jazzmaster guitars.

First introduced in 1960 as the Deluxe Model, it borrowed design elements from the Jazzmaster guitar. It was renamed the Jazz Bass as Fender felt that its redesigned neck—narrower and more rounded than that of the Precision Bass—would appeal more to jazz musicians.

The Jazz Bass has two single coil pickups with two pole pieces per string. As well as having a slightly different, less symmetrical and more contoured body shape (known in Fender advertising as the "Offset Waist Contour" body), the Jazz Bass neck is noticeably narrower at the nut than that of the Fender Precision Bass. While the Precision Bass was originally styled similarly to the Telecaster guitar, the Jazz Bass' styling was inspired by the Jazzmaster guitar, with which the Jazz shared its offset body and sculpted edges, which differentiate it from other slab-style bass bodies.

The original intention of the instrument was to appeal to upright bass players. The original Jazz Bass had two stacked knob pots with volume and tone control for each pickup. Original instruments with this stacked configuration are highly valued in the vintage guitar market. In late 1961, it received three control knobs: one volume knob for each pickup and a third to control the overall tone. Despite this new feature, many stacked knob models were made until about 1962. Another feature the initial models had were the "Spring Felt Mutes", which were present on basses from 1960 until 1962. The mutes were designed to dampen the overtones and the sustain; they were screwed in place between the bridge and aft pickup. Those felt mutes were not a tremendous success and were replaced by a cheaper, more simple foam mute glued underneath the bridge cover, as was used by the Precision Bass from 1963 onwards. Over the following years, as the use of mutes gradually declined, both the Precision and Jazz Bass models eventually began to be produced without bridge/tailpiece covers.

A number of cosmetic changes were made to the instrument when CBS purchased the Fender companies in 1965. During 1965/66, the Jazz Bass received bound rosewood fingerboards with pearloid dot position inlays (which replaced the older "clay"-style of the early 1960s) and oval-shaped tuning machines. Block-shaped fingerboard inlays and an optional maple fingerboard were introduced after 1966/67. At first, necks with rosewood fretboards received pearloid blocks/binding, and maple fretboard necks received black. Fender switched to pearloid blocks/binding on all necks in mid-to-late 1973. Fender also switched to the three-bolt neck "micro-tilt adjustable" neck and the "bullet" truss rod in mid-to-late 1974, before reverting to the more standard four-bolt neck fixing and dot-shaped fretboard markers in 1983. White pickup covers and a pickguard/control plate were introduced the same year. In 1986, Fender introduced the Japanese-made Fender Performer Bass, also with micro-tilt neck, designed by John Page and intended to be an Elite version of the Jazz Bass; however, the radical styling was not popular and production ceased the same year.

Two other changes that were more important to the tone of the instrument also occurred in the early 1970s. From 1960 until late 1970, the two pickups on the Jazz Bass were spaced 3.6 in (91 mm) apart. The bridge pickup was then moved .4 in (10 mm) closer to the bridge, creating a spacing of 4 in (100 mm). Many players believe that this change contributed to a somewhat brighter tone from the bridge pickup. According to Fender itself, this change happened in 1972. However, Fender's own history is clearly incorrect, as there are unquestionably examples of Jazz basses made in late 1970 that use the 4" pickup spacing. Both 3.6" and 4" spacing are found in Jazz basses made in 1971, and there are even a few Jazz basses made in 1972 that use the older 3.6" spacing. Around the same time, Fender began using ash for most of the instrument bodies. Prior to the early 70's, most Jazz basses had bodies made of alder, except for those that were finished in a clear or ("natural") finish - for those basses, ash was nearly always the wood of choice. In the early 70s, ash bodies became increasingly common, and by 1974 ash bodies were the rule, rather than the exception. Ash is generally thought to produce a somewhat brighter (and correspondingly less warm) tone than alder. By the mid-1970s, the combination of 4" pickup spacing and the use of heavier ash bodies with maple fingerboards combined to produce a notably brighter tone than that produced by Jazz basses from the 60s.

American Standard Jazz Basses produced between 1989 and mid-1994 featured a larger body shape, a 'curved' neck plate set into a chambered pocket for greater sustain and a 22-fret neck, similar to that of a Precision Bass Plus, with a standard vintage-style top-load bridge, two separate volumes and a master TBX tone circuit.

Usually known as "Boner" Jazz Basses, these early American Standard models (designed by George Blanda, who was Fender's senior R&D engineer during that period) were discontinued in 1994 and shouldn't be confused with the Fender Jazz Bass Plus, which has the same 22-fret neck design, but utilizes a different (downsized) body styling, Lace Sensor pickups, Schaller "Elite" fine-tuner bridge on the four-string model or Gotoh Hardware high-mass bridge on the 5-string model, and Phil Kubicki-designed active electronics. Unlike the Fender Precision Bass Plus, which had an optional maple neck, the Boner Jazz Bass was offered only with a rosewood fingerboard.