The Huincul Formation is a geologic formation of Late Cretaceous (Cenomanian to Early Turonian) age of the Neuquén Basin that outcrops in the Mendoza, Río Negro and Neuquén Provinces of northern Patagonia, Argentina. It is the second formation in the Río Limay Subgroup, the oldest subgroup within the Neuquén Group. Formerly that subgroup was treated as a formation, and the Huincul Formation was known as the Huincul Member.

The type locality of the Huincul Formation is near the town of Plaza Huincul in Neuquén Province after which the formation was named by Wichmann in 1929. This formation conformably overlies the Candeleros Formation, and it is in turn overlain by the Lisandro Formation.

The Huincul Formation is thought to represent an arid environment with ephemeral or seasonal streams. In some areas, it is up to 250 metres (820 ft) thick. It is mainly composed of green and yellow sandstones and can easily be differentiated from the overlying Lisandro Formation, which is red in color. The Candeleros Formation, underlying the Huincul, is composed of darker sediments, making all three formations easily distinguishable.

Dinosaur fossils are frequently found in the Huincul Formation. The titanosaurian sauropod Argentinosaurus huinculensis, one of the largest known land animals, is named after the formation. Another noteworthy Huincul dinosaur is the carcharodontosaurid theropod Mapusaurus roseae, which is regarded as one of the largest known terrestrial predators.

Apart from sauropods and theropods, rare fossils of iguanodonts and other ornithopods have been recorded in the formation. Ichnofossils (footprints) of abelisaurid theropods and hadrosaurs are also known.

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ornithischians of the Huincul Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Chakisaurus	C. nekul	Pueblo Blanco Natural Reserve	Lower	Multiple partial skeletons belonging to individuals of different ages	An elasmarian ornithopod; the first ornithischian named from the Huincul Formation

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Sauropods of the Huincul Formation
Genus	Species	Locality	Stratigraphic unit	Material	Notes	Images
Argentinosaurus	A. huinculensis	Las Overas		Seven dorsal vertebrae, partial sacrum, partial dorsal rib, fibula, and potentially other hindlimb bones	A titanosaur
Bustingorrytitan	B. shiva	Villa El Chocón.	Lower	Four specimens are known, including dentary and postcranial skeleton parts.	A titanosaur
Cathartesaura	C. anaerobica	La Buitrera	Lower	A fossil consists of a partial skeleton including vertebrae and limb bones.	A rebbachisaurid
Choconsaurus	C. baileywillisi	Villa El Chocón.	Lower	Partial skeleton without a skull, MMCh-PV 44/10.	A titanosaur
Chucarosaurus	C. diripienda	Violante farm.	Lower	A complete left humerus, partial left radius, complete left metacarpal II, left ischium, partial left femur and fibula, partial right tibia, and partial indeterminate metapodial.	A titanosaur.
Limaysaurus	L. tessonei	Villa El Chocón.	Lower		A rebbachisaurid
Sidersaura	S. marae	Barda Atravesada de Las Campanas	Lower	Two partial skeletons consist of a braincase fused to the skull roof and partial neurocranium, partial dorsal vertebrae, a dorsal rib, two metacarpals, a partial pelvic girdle including an incomplete ilium, ischia, and pubes, and the left femur and fibula fourteen caudal vertebrae with some haemal arches, a partial left scapula, right pubic peduncle, part of both tibiae and fibulae, and several bones from the feet, including metatarsals, phalanges, and ungual phalanges.	A rebbachisaurid

Theropods of the Huincul Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Aoniraptor	A. liberataem	Violante Farm	Lower	Sacral vertebra, six proximal caudal vertebrae, four mid-caudal vertebrae.	A fragmentary theropod originally described as a megaraptoran.
Gualicho	G. shinyae	Violante Farm	Lower	A partial skeleton lacking the skull along with several veterbraes, ribs, the left shoulder girdle, the left forelimb, the right lower arm, the lower ends of both pubic bones, thighbones, shinbones, calf bones, metatarsi and three toes of the right foot (Holotype MPCN PV 0001).	A theropod of uncertain affinities
Huinculsaurus	H. montesi	Aguada Grande	Upper	Several vertebrae	A noasaurid
Ilokelesia	I. aguadagrandensis	Aguada Grande	Upper	Fragmented skull and the axial, appendicular skeleton.	An abelisaurid
Mapusaurus	M. roseae		Upper (middle section of formation)	Multiple skeletal specimens.	A carcharodontosaurid
Meraxes	M. gigas	Las Campanas Creek	Lower	A nearly complete skull, pectoral and pelvic elements, partial forelimbs, complete hindlimbs, fragmentary ribs, and cervical and dorsal vertebrae, a sacrum, and several complete caudal vertebrae.	A carcharodontosaurid
Overoraptor	O. chimentoi	Violante Farm	Lower	Skeletal specimen consists of two phalanges and a metacarpal of the right hand, two hemal arches, the right scapula, the right ulna, a partial ilium, a partial pubis, two metatarsals from each foot, and several phalanges and unguals from the left foot.	A paravian.
Skorpiovenator	S. bustingorryi	Bustingorry's Farm	Lower	A preserved skeleton.	An abelisaurid
Taurovenator	T. violantei	Violante Farm	Lower	An isolated right postorbital.	A carcharodontosaurid
Tralkasaurus	T. cuyi	Violante Farm	Lower	An incomplete skeleton ( MPCA-Pv 815), which comprises a maxilla; dorsal, sacral, and caudal vertebrae; cervical ribs; and a badly-preserved pubis.	An abelisaurid

Apart from the taxa named here, fossils of unnamed squamates and neosuchian crocodyliforms have been discovered in the formation.

Non-dinosaur reptiles of the Huincul Formation
Genus	Species	Material	Notes	Images
Kaikaifilusaurus	K. sp.	Incomplete right dentary	An eilenodontine rhynchocephalian
Patagosphenos	P. watuku	Disarticulated skull with shoulder and limb fragments	An eilenodontine rhynchocephalian
Prochelidella	P. buitreraensis	Skull, two cervical vertebrae, partial left forelimb, right pelvic girdle, shell fragments	A chelid turtle

• List of fossil sites
• List of dinosaur bearing rock formations

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• Sánchez, María Lidia; Heredia, Susana; Calvo, Jorge O. (2006). "Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén" [Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group), Confluencia, Neuquén)]. Revista de la Asociación Geológica Argentina. 61: 3–18. Retrieved 2019-02-16.
• Wichmann, R (1929). "Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén ("The dinosaur-bearing strata and their upper limit in eastern Neuquén Territory")". Dirección General de Geología, Minería e Hidrogeología Publicación. 32: 1–9.