The gill arch, the internal supporting skeleton of an individual gill, is a plate on which the stamens and gill lobes are located.

The paired arc-shaped cartilaginous plates of the gill skeleton of fish. Fish have from 3 to 7 gill arches, each divided into four movably connected sections and located between the gill slits; gills develop on the outer surface of the gill arch. Many sharks have one or two pairs of small lip cartilages in front of the jaw arc, which are probably reduced gill arches; thus, the jaw arc may have been formed from a third gill arc.

Gill arches are a system of skeletal elements of the pharynx in cyclostomes and fishes, each of which encloses the pharynx in a semicircle. The majority of modern fish have five gill arches, roundbearers and some sharks have as many as seven. Due to the reduction of the distal (located closer to the tail) the number of gill arches in bony fish may be reduced to three. Anatomically, the gill arches of round-breasted, cartilaginous, sturgeon and bivalve fish are cartilaginous, while those of bony fish are bony. Fully formed gill arches of fish consist of 4 movably connected segments. In bony fish the fifth gill arch, called the lower pharyngeal bone, is usually rudimentary, but in carp fish it bears teeth and is quite massive.