Hyracotherium (/ˌhaɪrəkoʊˈθɪəriəm, -kə-/ HY-rək-o-THEER-ee-əm; "hyrax-like beast") is an extinct genus of very small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation.

This small, fox-sized animal is (for some scientists) considered to be the earliest known member of Equidae before the type species, H. leporinum, was reclassified as a palaeothere, a perissodactyl family related to both horses and brontotheres.

[2] The first fossil identified as being of this genus, holotype specimen BMNH M16336, was found in the cliffs of Studd Hill near Herne Bay, Kent, and described by the paleontologist Richard Owen in a paper read to the Geological Society of London on 18 December 1839 as a "small mutilated cranium about the size of that of a hare".

[3] In his formal description published by the Geological Society in 1841, Owen wrote "Without intending to imply that the present small extinct Pachyderm was more closely allied to the Hyrax than as being a member of the same order, and similar in size, I propose to call the new genus which it unquestionably indicates, Hyracotherium, with the specific name leporinum.

[6][7] Most other species of Hyracotherium are still regarded as equids, but they have been placed in several other genera, such as Arenahippus, Minippus, Sifrhippus, Xenicohippus, Pliolophus, Protorohippus and the resurrected Eohippus.