The Titicaca orestias, Lake Titicaca orestias, or Lake Titicaca flat-headed fish (Orestias cuvieri), also known by its native name amanto, is a likely extinct freshwater killifish from Lake Titicaca in South America. It belongs in the pupfish genus Orestias, endemic to lakes, rivers and streams in the Andean highlands. With a total length of up to 27 cm (10.6 in), it was the largest member in that genus. In the hope that an undiscovered population remains, it is listed as Critically Endangered, possibly extinct by the IUCN. Despite its common name, it is not the only Orestias from Lake Titicaca.

Its mouth was nearly turned upwards, thereby giving the flat head a concave shape. The head took up nearly a third of the whole body length. The upperside was greenish-yellow to umber. The lower jaw was black. Its scales were oddly light coloured at their centre. The scales of the young were blotched.

The Titicaca orestias became extinct due to competition by introduced trout like the lake trout, brown trout, or the rainbow trout as well as Argentinian silverside from the 1930s to the 1950s. A survey in 1962 failed to find any Titicaca orestias.

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