Anostomus ternetzi, the red mouth headstander,[1] is a fish in the family Anostomidae.

[1][2][3] The fish is named in honor of ichthyologist and naturalist Carl Ternetz (1870–1928), who collected the type specimen.

[4] It can grow to 12 cm (4.7 in) total length.

[2] Anostomus ternetzi is widespread in South America: it is found in the Orinoco, Araguaia and Amazon River basins (Brazil, Colombia, and Venezuela) as well as in coastal rivers of Guianas.

[1][2] It occurs in both black and clear water rivers.