Eileanchelys is an extinct genus of primitive turtle from the Middle Jurassic (Bathonian) period some 164 million years ago of Britain.

The species was named in honour of Dr. Michael Waldman who found its remains, as well as the first Scottish Jurassic mammal, after rediscovering the Cladach a'Ghlinne locality.

[1] Eileanchelys is characterized by the following features: the presence of nasal; elongated postorbital skull;[2] absence of flooring of the cavum acustico-jugulare; processus interfenestralis of the opisthotic more slender than that of more basal forms but more robust than that of crown-group turtles; separate openings of the canalis cavernosum and canalis stapedio-temporalis present within the cavum acustico-jugulare; a reduced thickness of the basicranium floor comparable with that of crown-group turtles; well-developed antrum postoticum; flat and horizontal vomer that is free of contacts for most of its length except at its extremities and along a short suture with the prefrontal; absence of processus trochlearis oticum; posteroventrally open incisura columellae auris; at least eight neurals (an additional plate between neural 8 and suprapygal 1 may be a ninth neural or a supernumerary suprapygal), two broad suprapygals, and eight costals present; absence of carapacial or plastral fontanelle in adult individuals; one short but broad cervical scute present; vertebral scutes wider than pleurals; vertebral 3–4 sulcus on neural 6; reduced cleithrum present; arrow-shaped entoplastron that does not separate the epiplastra anteriorly; one pair of mesoplastra that meet medially; one small pair of extragulars present; and anal scute that does not reach the hypoplastron.

The below cladogram illustrates the relationships of basal testudinata:[1] Hypothetical ancestor Proganochelys quenstedti Palaeochersis talampayensis Australochelys africanus Proterochersis robusta Kayentachelys aprix Eileanchelys waldmani Heckerochelys romani Condorchelys antiqua Meiolania platyceps Mongolochelys efremovi Testudines Eileanchelys lived in the Kilmaluag Formation, which has a Late Bathonian age.

The formation is made up entirely of mudstone, shale and some limestone, and, as many aquatic types of animals have been found in it and land vertebrates are rare, it was almost certainly marine.

Therefore, Eileanchelys was most likely was an aquatic turtle,[2] swimming throughout lagoons and lakes, rather than terrestrial animal that died in a body of water.