Regaliceratops (meaning "Royal horned face") is a monospecific genus of chasmosaurine ceratopsid dinosaur from Alberta, Canada that lived during the Late Cretaceous (middle Maastrichtian stage, 68.5 to 67.5 Ma) in what is now the St. Mary River Formation.

The type and only species, Regaliceratops peterhewsi, is known only from an adult individual with a nearly complete skull lacking the lower jaw, which was nicknamed "Hellboy".

The specimen was nicknamed "Hellboy" due to the difficult and time-consuming excavation, in addition to the hard matrix, and the presence of small postorbital horncores with resorption pits.

The specimen represents an adult individual as the cranial elements are fused together and the bone surface texture is rugose, unlike that of juvenile and subadult ceratopsids.

[1] The skull was co-collected and prepared by Royal Tyrrell Museum senior technician Darren H. Tanke over a 17 month period.

[2] Brown & Henderson (2015) diagnosed Regaliceratops based on the presence of a single, midline epiparietal ossification that is offset from the plane of the frill and other epiparietals towards the rostrum with parietals projecting towards the posterior end that have a roughly triangular transverse cross-section; a prominent midline ridge on that parietal that merges with the median epiparietal; paired epiparietal ossifications that are long, flat, and roughly pentagonal shaped; a prominent postorbital ridge that runs diagonally from the supraorbital horncore to the base of the squamosal; parietal fenestrae that are small in size to orbit as in Kosmoceratops; and nasal horncores that are larger than the postorbital horncores as in Chasmosaurus belli and Vagaceratops.

The fossa is further thinned at the caudal portion and is spread throughout by the presence of a large interpremaxillary fenestra as in Anchiceratops, Arrhinoceratops and Triceratops.

Unlike Campanian chasmosaurines such as Chasmosaurus and Utahceratops, the caudoventral process of Regaliceratops tapers caudally without forking, and inserts between the maxilla and nasal towards the sides.

The rostrodorsal margin of the orbital rim consists of the palpebral, and swells towards the sides and rostrums which forms an antorbital buttress.

Unlike Kosmoceratops, the postorbital horncore of Regaliceratops is arranged slightly caudal to the orbit but shares the narrow base.

A prominent postorbital ridge is present caudomedially to the horncore which is equivalent to the supraorbital squamosal scale row.

[1] Brown & Henderson (2015) originally placed Regaliceratops within Triceratopsini, in a polytomy with Eotriceratops, Ojoceratops, and a clade containing more nested taxa such as Nedoceratops, Titanoceratops, Triceratops and Torosaurus.

[1] Regaliceratops peterhewsi Eotriceratops xerinsularis Ojoceratops fowleri Titanoceratops ouranos Nedoceratops hatcheri Torosaurus latus Torosaurus utahensis Triceratops horridus Triceratops prorsus Regaliceratops is known from the St. Mary River Formation which has been dated to the middle Maastrichtian stage of the Late Cretaceous period.

Ferns, ginkgoes, conifers, Trapa-like plants, sabaloid palms and at least six types of large monocot leaves are known from the formation.

[5][6][7] The fauna of the St. Mary River Formation consists of the nodosaurid ankylosaur Edmontonia, the leptoceratopsid ceratopsian Montanoceratops, the centrosaurine ceratopsid Pachyrhinosaurus, a ceratopsid that was previously considered to be Anchiceratops, the albertosaurine tyrannosaurid Albertosaurus, the saurornitholestine dromaeosaurid Saurornitholestes, the troodontid Troodon,[8] the mammals Cimolomys, Meniscoessus, Mesodma, Cimolodon, Pediomys, Didelphodon and Eodelphis, the fish Myledaphus and Lepisosteus, the crocodylomorph Leidyosuchus, and the choristodere Champsosaurus.