Gymnogeophagus missioneiro is a species of geophagine cichlid. It inhabits parts of the Uruguay and Río Negro rivers. It is characterised by the absence of supraneural bones, the presence of a forward spine in its first dorsal fin pterygiophore, the absence of an oblique bar between the eye and nape, possessing a black marking near the dorsal fin origin that projects to its dorsum, as well as other features.[1]