An acoustic guitar whose sound is produced by one or more spun metal cones (resonators) instead of the wooden soundboard (guitar top/face). Resonator or resophonic guitars were originally designed to be louder than regular acoustic guitars, which were overwhelmed by horns and percussion instruments in dance orchestras. They became prized for their distinctive sound, however, and found life with several musical styles (most notably bluegrass and the blues) well after electric amplification solved the issue of inadequate guitar sound levels.

Resophonic guitars are of two styles:

• square-necked guitars played in steel guitar style
• round-necked guitars played conventional guitar style or lap steel guitar style

There are three main resonator designs:

• the Tricone, with three metal cones, designed for the first National
• the single cone 'biscuit' design of other National instruments
• the single inverted-cone design (aka 'spider bridge') of the Dobro

Many variations of all these styles and designs have been produced under many brands. The body of a resophonic guitar may be made of wood, metal, or occasionally other materials. Typically there are two main sound holes, positioned on either side of the fingerboard extension. In the case of single cone models, the sound holes are either both circular or both f-shaped, and symmetrical. The older Tricone design has irregularly shaped sound holes. Cutaway body styles may truncate or omit the lower f-hole.