Melanorivulus is a genus of South American freshwater fish in the family Rivulidae.

Most species are endemic to the Río de la Plata, eastern Amazon (west to Tapajós basin), Tocantins–Araguaia and São Francisco basins in Brazil, but a few members of this genus range west into Bolivia, south into Paraguay and Argentina, and east to Parnaíba and Sergipe in northeastern Brazil.

[2][3][4][5] They inhabit shallow waters, generally 5–30 cm (2–12 in) deep, at the margins of streams in open or fairly open habitats like the Cerrado or Cerrado–Amazon transition.

[6] Similar to closely related genera such as Anablepsoides, Atlantirivulus, Cynodonichthys and Laimosemion, Melanorivulus are jumpers and non-annual killifish.

[3][5] Until 2011, Melanorivulus were included in Rivulus,[7] and some prefer to maintain them in that genus.