Simpsonichthys is a genus of killifish from the family Rivulidae the species of which are endemic to temporary freshwater habitats like ponds in the upper Paraná, upper Araguaia, upper Jequitinhonha and São Francisco basins on the central Brazilian Plateau.

[1] They are small annual killifish that reach up to 5.5 cm (2.2 in) in standard length.

[2][3] As delineated by Fishbase the following species are included within the genus Simpsonichthys: Simpsonichthys sensu lato was formerly one of the larger genera in the family, but four former subgenera were elevated to full genera in 2010: Hypsolebias, Ophthalmolebias, Spectrolebias and Xenurolebias.

[5] Some uncertainty remains, with one genetic study supporting them,[6] while another genetic study indicates that Simpsonichthys (sensu stricto), Hypsolebias and Spectrolebias are not monophyletic.

[7] With these as separate genera, there are currently 9 recognized species in Simpsonichthys:[1][2] The name of this genus is a compound of the name of a friend of Antenor Leitão de Carvalho's, Charles J. Simpson of San Francisco, and the Greek for fish, ichthys.