A resonator guitar or resophonic guitar is an acoustic guitar whose sound is produced by one or more spun metal cones (resonators) instead of the wooden sound board (guitar top/face). Resonator guitars were originally designed to be louder than conventional 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 also blues) well after electric amplification solved the issue of inadequate guitar sound levels.

Resonator guitars are of two styles: square necked guitars designed to be played in steel guitar style, and round necked guitars, which may be played in either the conventional classical guitar style or in the lap steel guitar style.

There are three main resonator designs: The "tricone" ("tri" in reference to the three metal cones/resonators) design of the first National resonator guitars, the single cone "biscuit" design of other National instruments, and the single inverted-cone design of the Dobro.