Tupandactylus (meaning "Tupâ or Tupan finger", in reference to a personification of the Tupi supreme deity) is a genus of tapejarid pterodactyloid pterosaur from the Early Cretaceous Crato Formation of Brazil. It is known from two species, T. imperator and T. navigans, though it has been suggested that there is only a single, highly sexually dimorphic species (which would then be T. imperator). T. imperator was described in 1997 by D. A. Campos and Alexander W. A. Kellner, who assigned it to Tapejara. Six years later, T. navigans was named and also assigned to Tapejara. In 2007, two efforts to reallocate both species to a new genus were made, and ultimately the name Tupandactylus came into use.

The larger Tupandactylus species, T. imperator, has an estimated wingspan of 3–4 m (9.8–13.1 ft) and may have stood 1.5 m (4.9 ft) tall when measured to the tip of its crest, whereas the smaller T. navigans had a wingspan of about 2.7 m (8.9 ft). Like other tapejarids, Tupandactylus had a large head crest, formed by keratinous fibres and supported by a dorsal extension of the rostrum and a rearward extension of the parietal bone. In T. imperator, the crest was large and rounded, whereas in T. navigans, it was tall and vertical. An additional crest was formed by a projection at the front of the lower jaw. The anatomy of Tupandactylus was standard for a tapejarid, with a large opening formed from the combination of the nasal cavity and the antorbital fenestra, and an eye socket set fairly low in the skull.

The holotype specimen of Tupandactylus is MCT 1622-R, a skull and partial lower jaw, found in the Crato Formation, dating to the boundary of the Aptian-Albian stages of the early Cretaceous period, about 112 Ma ago. It was initially described as a species of Tapejara, T. imperator, by D. A. Campos and Alexander W. A. Kellner in 1997. A second taxon, T. navigans, was named in 2003. In 2007, two efforts to reassign them to a new genus were made. One, by David Unwin and David Martill, would have seen them both assigned to the new genus "Ingridia"; the other, by Campos and Kellner, erected the genus Tupandactylus; ultimately, the latter name was used, since the publication by Unwin and Martill was published in a book months after the competing study. The genus name Tupandactylus derives from the name of the Tupí-Guaraní "Tupâ" or "Tupan", referring to a manifestation of the supreme deity Nhanderuvuçu which takes the form of thunder, and the Greek daktylos ("finger"). A second species of Tupandactylus, T. navigans, was named in 2003; like the type species, it, too, was initially assigned to Tapejara.

A 2021 study describing a very complete T. navigans specimen suggested that the two species might represent different sexes of one sexually dimorphic species, but cautioned that further study was needed to test this.

Tupandactylus imperator has been estimated to have had a wingspan about 3 to 4 m (9.8 to 13.1 ft), while T. navigans is smaller, with a wingspan of 2.7 m (8.9 ft). In 2013, Mark P. Witton suggested T. imperator had a wingspan of about 3 m (9.8 ft), and a standing height of 1.5 m (4.9 ft), when measured to the tip of its head crest.

Tapejarids overall were characterised by short faces, the product of an abbreviated rostrum (snout) and a downturned jaw tip. As a pterodactyloid, Tupandactylus bore a so-called nasoantorbital fenestra, a structure created by the fusion of the naris (nasal cavity) and antorbital fenestra. When viewed from a lateral (side) view, the premaxilla formed a triangular plate above the nasoantorbital fenestra. The premaxillas and maxillas of pterodactyloids formed a single unit, the premaxillomaxilla, whose fusion occurred early in ontogeny. The anterior (front) and ventral (lower) margins of the resultant structure, as well as the dentary (the front portion of the lower jaw), were covered in a rhamphotheca, or beak. Rhamphotheca are known from multiple Tupandactylus specimens. The orbit (eye socket) was pear-shaped, and as in other azhdarchoids, was positioned below the dorsal (upper) margin of the nasoantorbital fenestra; however, whereas some taxa such as Caupedactylus had very low orbits, the orbit of Tupandactylus was more akin to that of Caiuajara and Tapejara. The dentary had a mandibular symphysis which was slightly downturned towards the front. Like the skull, the dentary was crested. In T. imperator, the dentary crest is straight, whereas in T. navigans it is recurved.

Tupandactylus is notable for its large cranial crest, composed partly of bone and partly of soft tissue fibres, likely keratin. The crest was supported by a raised process on the premaxillomaxilla, often itself referred to as a crest, and a bony prong extending from the back of the head, formed from the parietal bone. The crest shapes of the two species differed substantially. T. imperator had a large, rounded crest, fairly backswept, with an irregular rear margin, and with a length and height equal to about one-third of its total wingspan; T. navigans, meanwhile, had a more vertical cranial crest, with a straighter posterior (rear) edge, and a blunt posterior skull face, unlike other tapejarids.

Hyoid bones are known from both species of Tupandactylus, ceratobranchials in both instances. Little data exists on the hyoid apparatus in pterosaurs, though from what can be seen, those of Tupandactylus are typical for the clade.