Apataelurus ("false cat") is an extinct genus of saber-toothed placental mammals from the extinct family Oxyaenidae, that lived in North America and East Asia during the Middle Eocene, 45-42 million years ago. This genus was defined by teeth that were well-adapted to a carnivorous diet. A distinct feature described was a long upper canine tooth that resembled a saber tooth. There are two species currently described: Apataelurus kayi, the type species, and Apataelurus pishigouensis, discovered in 1986.

As a large, leopard-sized predator, Apataelurus dominated the Uinta Formation area. It was adapted to taking on large prey with more struggling motion tolerant muscles in its mouth, allowing it to attack large prey that would fight back. It was closely related to other Machaeroidinae, such as Diegoaelurus vanvalkenburghae. Apataelurus and other species within the Uinta Basin emerged during a major transitional period between the reduction in tropical zones and the increase in temperate and subtropical biomes. Apataelurus was a more derived member of Oxyaenidae, and lived in the middle to late Lutetian age.

A. kayi was originally discovered by William Berryman Scott in Wagonhound Canyon at the Uinta Formation of the Uinta Basin, Utah. It was described and published in May 1938 as a "problematical, cat-like mandible". A. kayi was described from two separate halves of a lower jaw, the left half containing two of the cheek teeth, and the right half with four cheek teeth.

Apataelurus originates from Greek, with "apat" (false or tricky) and "aelurus" (cat or feline). A. kayi was further described in A Remarkable Sabretooth-Like Creodont From the Eocene of Utah, also by W.B. Scott. A. kayi was named for American paleontologist J. Leroy Kay.

The second species, Apataelurus pishigouensis, was discovered at the Hetaoyuan Formation in Henan, China in 1986 by Tong Yongsheng and Lei Yizhen. A. pishigouensis was named for the Pishigou fossil site, where it was discovered by Tong and Lei. A. pishigouensis was originally named Propterodon pishigouensis, under Hyaenodonta, but a study by S.P. Zack in 2019 reclassified the species into the genus Apataelurus and family Oxyaenidae.

Collected Apataelurus specimens consist exclusively of remains of the lower jaw. The largest find is an almost complete lower jaw, which contains part of the rear teeth. Based on the existing dental sockets, a dental formula with two incisors, one canine, four premolars, and two molars was likely present.

The lower jaw was 14.9 cm (5.9 in) long and 2.7 cm (1.1 in) high below the first molar. Towards the front, the horizontal bony body became noticeably higher and ended in the area of the symphysis in a flange-like projection pointing downwards. Such projections are characteristic of predators whose upper canines were significantly elongated, as is the case, for example, in saber-toothed cats. They protected the canine tooth when the jaw was closed. A. pishigouensis and A. kayi share a well developed paraconid (a major cusp on the inner edge of the cheek teeth).

The ascending ramus (lower part of the jaw, to which pterygoid muscles attach to) featured a deep masseteric fossa (flat bone surface) with sharp edges to which the masseter muscle attached. The articular process and coronoid process were both significantly reduced in size. Both the protrusion of the anterior segment of the mandible and the low position of the coronoid process were more pronounced in Apataelurus than in the closely related Machaeroides.