Deinonychosauria is a clade of paravian dinosaurs that lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica, with fossilized teeth giving credence to the possibility that they inhabited Australia as well. This group of dinosaurs are known for their sickle-shaped toe claws and features in the shoulder bones.

Deinonychosauria is commonly defined as all dinosaurs more closely related to dromaeosaurids (such as Deinonychus antirrhopus) than to birds (such as Passer domesticus). It traditionally includes the families Dromaeosauridae and Troodontidae, which each possess enlarged "sickle claws". Troodontids may instead be closer to birds than to dromaeosaurids, however, so they would lie outside Deinonychosauria under that hypothesis. This would also render Deinonychosauria equivalent to Dromaeosauridae, under a broad definition of the family. As the structure of the paravian family is still undergoing debate, the components of Deinonychosauria is unstable beyond dromaeosaurids.

In 1866 Ernst Haeckel created the now-deprecated subclass of birds known as Sauriurae (meaning "lizard tails" in Greek). It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae ("bird tails", from ornithes and ourai.). The distinction Haeckel referred to in this name is that Archaeopteryx possesses a long, reptile-like tail, while all other birds known to him had short tails with few vertebrae, fused at the end into a pygostyle. The unit was not much referred to, and when Hans Friedrich Gadow in 1893 erected Archaeornithes for basically the same fossils, this became the common name for the early reptile-like grade of birds. (The prefix "archaeo-" signifies in ancient Greek the "ancient.") This was followed by Alfred Romer (1933) and subsequent authors through most of the 20th century. According to Romer, the Archaeornithes are characterised by having clawed wings, a reptilian style ribcage without a large carina and the presence of a long, bony tail. The known members of the group by the time of its erection were Archaeopteryx and Archaeornis. The two are now thought to represent a single species, Archaeopteryx lithographica, the Archaeornis being the Berlin specimen of Archaeopteryx. It was in 1888 the German anatomist Max Fürbringer created the order Archaeopterygiformes, though the unit was not used as much as Archaeornithes. Due to the popularity of Archaeornithes as well as Archaeopterygidae being recognized as the only family in this clade, Sauriurae, Archaeornithes, and Archaeopterygiformes are considered to be redundant arbitrary names that can be synonymous.

During the dinosaur renaissance, the American palaeontologist John Ostrom had published a series of papers arguing that birds are highly derived dinosaurs, after undertaking comparisons between the then-newly discovered Deinonychus (from deinon & onyx denoting "terrible" & "nail") and Archaeopteryx (from archaeon & pteryx denoting "ancient" & "wing"), and noting their similarities in the wrist and shoulder bones. In his 1988 book Predatory Dinosaurs of the World, Gregory S. Paul classified dromaeosaurids in Archaeopterygidae. Paul states that:

Many theropods have been united into new groups... but the placement of Archaeopteryx and the sickle-clawed dromaeosaurs in the same family is by far the most radical–yet it is also one of the most necessary... how alike, in detail after detail, dromaeosaurs and Archaeopteryx were.

The name Deinonychosauria was coined by Ned Colbert and Dale Russell in 1969, and defined as a clade (all theropods closer to dromaeosaurids than to birds) by Jacques Gauthier in 1986. Through the early 2000s, the consensus among paleontologists was that dromaeosaurids were most closely related to the troodontids, and with the troodontids, deinonychosaurians were turned into the sister taxon to avialans, and therefore the closest relatives of avialan birds. In 2012, Turner et al. conducted a phylogenetic analysis (using a dataset of 474 characters scored for 111 taxa) that found Deinonychosauria to be monophyletic.

Nonetheless, several more recent studies have cast doubt on the hypothesis that dromaeosaurids and troodontids were more closely related to each other than either was to birds. A more robust 2013 study by Godefroit et al. (using a dataset of 1,500 characters scored for 358 taxa) found that troodontids were possibly more closely related to birds than to dromaeosaurids; forcing troodontids to remain in a monophyletic Deinonychosauria required four extra steps in the analysis, making this result less likely, but not implausible. Because Deinonychosauria was originally defined as all animals closer to dromaeosaurids than to birds without specific reference to troodontids, Deinonychosauria is a synonym of Dromaeosauridae if Troodontidae is closer to birds.

With the description in 2019 of the Late Jurassic genus Hesperornithoides, Hartman et al., using every named Mesozoic maniraptoromorph (with the addition of 28 unnamed specimens), which they scored 700 characters and 501 operational taxonomic units, found that most of the anchiornithids are members of Archaeopterygidae, Halszkaraptorinae and Unenlagiinae are in a redefined family Unenlagiidae, and a Dromaeosauridae sensu stricto is the sister taxon of Troodontidae. The authors opted for Deinonychosauria (defined as dinosaurs closer to Deinonychus antirrhopus than to Passer domesticus) over "Archaeopterygiformes".