Prestosuchus (meaning "Prestes crocodile") is an extinct genus of pseudosuchian in the group Loricata, which also includes Saurosuchus and Postosuchus. It has historically been referred to as a "rauisuchian", and was the defining member of the family Prestosuchidae, though the validity of both of these groups is questionable: Rauisuchia is now considered paraphyletic and Prestosuchidae is polyphyletic in its widest form.

The holotype of Prestosuchus chiniquensis was discovered by Wilhelm Rau alongside the holotype of Rauisuchus tiradentes in the Santa Maria Formation at the Paleontological Site Chiniquá, near the city of São Pedro do Sul in 1928 or 1929, and the fossils were shipped back to Germany for study by the German paleontologist Friedrich von Huene. Von Huene named the genus Prestosuchus in 1938 in honor of Vicentino Prestes de Almeida. This site is located in the geopark of Paleorrota.

The first two specimens of Prestosuchus to be described were found at the Weg Sanga site near the town of São Pedro do Sul in Rio Grande do Sul, Brazil. One specimen was a partial skeleton including a jaw and snout fragments, and its bones were labelled SNSB-BSPG AS XXV 1-3, 5-11, 28-41, and 49. This specimen was later designated as the lectotype of Prestosuchus chiniquensis in 1972. Another specimen, SNSB-BSPG AS XXV 7, consists of the upper part of the hip and sacrum and was designated the paralectotype of the species. Although Kischlat (2000) assigned the paralectotype hip material to "Karamuru vorax", its original referral to P. chiniquensis was upheld by Desojo et al. (2020) when the specimen was redescribed along with the lectotype. These two specimens were originally described by von Huene (1938) and are stored at the Bavarian State Collection for Palaeontology and Geology (Bayerische Staatsammlung für Paläontologie und Geologie, BSPG) institute of the Bavarian Natural History Collections (Staatliche Naturwissenschaftliche Sammlungen Bayerns, or SNSB) in Munich, Germany.

Huene described several more Prestosuchus-like reptiles shortly afterwards, although he did not consider them to be the same species as Prestosuchus chiniquensis. One specimen, with its fossils labelled as SNSB-BSPG AS XXV 131-139, was given its own genus and species: Procerosuchus celer. Another specimen, with its fossils labelled SNSB-BSPG AS XXV 13–24, 26–27, and 44–48, was designated as a second species of Prestosuchus, Prestosuchus loricatus. Some authors have considered both of these specimens to belong to P. chiniquensis, while others have gone as far as to consider not only Procerosuchus celer a separate genus, but also "Prestosuchus" loricatus.

Kischlat (2000) referred to "Prestosuchus" loricatus as "Abaporu" loricatus, but this name was never formalized and has not been used since. In the same paper, several Prestosuchus specimens, including the paralectotype of P. chiniquensis and the "Porto Alegre specimen" (i.e. UFRGS-PV-0156-T), were named as a different new genus, "Karamuru vorax". However, this name was also poorly defined and never formalized, so "Karamuru vorax" is considered a nomen nudum along with "Abaporu" loricatus. Kischlat (2023) later proposed the new genus name Huenesuchus for Prestosuchus chiniquensis. Although he admitted that Prestosuchus is a valid name, he preferred to replace that name under the argument that a type species was not explicitly established by von Huene along ICZN guidelines. Other paleontologists have informally disagreed with this argument, and publications relevant to Prestosuchus, starting with Kuhn (1961), have consistently treated P. chiniquensis as a valid type species. McDavid (2025) formally discussed the issue, citing Prestosuchus as the proper generic name since it had been diagnosed by Oskar Kuhn in 1961. In a later publication Pêgas, Bandeira & Silva (2025) noted that Kuhn (1961) provided references to purported descriptions of the genus in Huene (1942) and Hoffstetter (1955), but argued that these works (and, as a consequence, Kuhn's publication as well) actually lack any sort of statement of "characters that are purported to differentiate the taxon" that would fulfill the criteria from the Article 13.1. of ICZN. Instead, the authors pointed to Krebs (1976) as the publication fulfilling the criteria of the Code and making the name Prestosuchus nomenclaturally available.

Desojo & Rauhut (2024) redescribed the remains of "Prestosuchus" loricatus and determined that it was a valid species of poposauroid, not closely related to Prestosuchus chiniquensis. In accordance with this finding, "Prestosuchus" loricatus was placed into a new genus, Schultzsuchus, named after Cesar Schultz.

Four specimens are stored at the Universidade Federal do Rio Grande do Sul (UFRGS) in Porto Alegre. The first to be described was UFRGS-PV-0156-T, a massive and well-preserved skull discovered along with most of a vertebral column at the Pascual Sanga outcrop in Candelária. It was originally described by Barberena (1978) and has experienced much discussion as to its relations to the original Munich specimens. A more complete partial skeleton from Vale Verde, UFRGS-PV-0152-T, was studied by Nesbitt (2011) along with the Munich lectotype and UFRGS-PV-0156-T. It is anatomically similar to the latter specimen but has yet to be fully described.

The most complete UFRGS specimen is UFRGS-PV-0629-T, a partial skeleton from Dona Francisca which was originally described in a thesis by Mastrantonio (2010). This specimen has been the subject of braincase (2013), skull (2019), and postcranial (2024) descriptions, as well as hip muscle reconstructions. The least complete UFRGS specimen is UFRGS-PV-0473-T, an isolated braincase which may be from the "Posto de Gasolina" outcrop in Dona Francisca. Porto Alegre has one additional Prestosuchus specimen unaffiliated with the UFRGS: MCP-146, a portion of the hip area stored at the Museu de Ciências e Tecnologia of Pontífícia Universidade do Rio Grande do Sul.