Desmatochelys (from Greek δεσμός desmos 'link' + χέλῡς khelus ‘tortoise’) is an extinct genus of sea turtles belonging to the family Protostegidae.

[9][10][8] As of 2019, Desmatochelys contains the two previously stated species, is within the family Protostegidae, and is placed along the stem of Chelonioidea - in other words, it is considered a basal turtle genus.

This specimen was from the Late Cretaceous Benton Formation and included a nearly complete skull and lower jaw as well as pieces of the limbs, carapace, and plastron.

[15] Due to its incomplete features and lack of information on the geological setting, the species remained undescribed at the museum of University of California, Berkeley.

[17] The fossils were preserved in the collections of the Centro de Investigaciones Paleontológicas in Villa Leyva and the University of California Museum of Paleontology.

Formal description was done by Edwin Cadena at the Senckenerg Research Institute, and James Parham at the California State University.

This placed its age around 120 million years, making it the oldest known sea turtle, a title which was previously held by Santanachelys gaffneyi.

[4] Members of the genus are characterized by the extended skull roof, large nasal bones, and a paddle-like humerus, as well as a distinct body shell or carapace and reduced plastron like other protostegids.

[19] Specimens of Desmatochelys have been found in Nebraska, South Dakota, Kansas, Arizona, Canada, Colombia, and Mexico.