The Portezuelo Formation is a geologic formation of Late Cretaceous (Late Turonian to Early Coniacian) age, outcropping in the Mendoza, Río Negro and Neuquén provinces of Argentina. It is the fourth-oldest formation in the Neuquén Group and the older of the two formations in the Río Neuquén Subgroup. Formerly, that subgroup was treated as a formation, and the Portezuelo Formation was known as the Portezuelo Member.

The type locality of the Portezuelo Formation is the mountain range known as Sierra del Portezuelo in Neuquén Province. This formation conformably overlies the Lisandro Formation of the Río Limay Subgroup. In the top layers it grades into the Plottier Formation, the younger formation within the Río Neuquén Subgroup.

Sandstones and siltstones, probably deposited under fluvial conditions, make up the Portezuelo Formation. There are also occasional cemented claystone deposits, as well as numerous paleosols (fossil soils). The formation varies between 95 and 130 metres (312 and 427 ft) thick throughout its range.

Many dinosaur fossils have recently been described from this formation, as well as remains of several other types of animals:

• teleosteid fish including Leufuichthys
• ceratodontiform lungfish including Chaoceratodus
• abundant and diverse turtles including Portezueloemys and a species of Prochelidella
• titanosaurian sauropods including Futalognkosaurus, Baalsaurus, Malarguesaurus, Muyelensaurus
• dromaeosaurid theropods including Neuquenraptor, Unenlagia, Pamparaptor
• megaraptorid theropods (including Megaraptor and an unnamed form)
• an alvarezsaurid theropod Patagonykus
• abelisauroid theropods (Elemgasem, a possible noasaurid and an abelisaurid)
• An elasmarian ornithopod (Macrogryphosaurus)
• notosuchian crocodylomorphs (Comahuesuchus, Lomasuchus, Patagosuchus)
• several other theropods, including a modern, possibly galliform bird
• ornithopods including possible iguanodonts
• a possible azdarchoid pterosaur Argentinadraco

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

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