Balaur bondoc is a species of paravian theropod dinosaur from the late Cretaceous period, in what is now Romania. It is the type species of the monotypic genus Balaur, after the balaur (Romanian pronunciation: [baˈla.ur]), a dragon of Romanian folklore. The specific name bondoc (Romanian pronunciation: [bonˈdok]) means "stocky", so Balaur bondoc means "stocky dragon" in Romanian. This name refers to the greater musculature that Balaur had compared to its relatives. The genus, which was first described by scientists in August 2010, is known from two partial skeletons (including the type specimen). Some researchers suggest that the taxon might represent a junior synonym of Elopteryx.

Fossils of Balaur were found in the Densuș-Ciula and Sebeș Formations of Cretaceous Romania which correspond to Hațeg Island, a subtropical island in the European archipelago of the Tethys sea approximately 70 million years ago. Hațeg Island is commonly referred to as the "Island of the Dwarf Dinosaurs" on account of the extensive fossil evidence that its native dinosaurs exhibited island syndrome, a collection of morphological, ecological, physiological and behavioural differences compared with their continental counterparts. Examples included island gigantism of Hatzegopteryx, island dwarfism of the titanosaur Magyarosaurus dacus, and a reduction in flight capacity in Balaur.

Balaur may have been a basal avialan, a group that includes modern birds based on phylogenetic analysis, though some researchers still include the genus within Velociraptorinae as its original description or alternatively within Unenlagiinae. This reduction in flight capacity is also seen in extant island birds including the ratites and insular barn owls as well as the extinct moa of New Zealand and the extinct dodo of Mauritius.

The first small bones belonging to Balaur bondoc consisted of six elements of the front limbs. Named specimens FGGUB R. 1580–1585, these were discovered in 1997 in Romania by Dan Grigorescu, but the morphology of the arm was so unusual that scientists could not correctly combine them, mistaking them for the remains of an oviraptorosaur. The first partial skeleton was discovered in September 2009 in Romania, approximately 2.5 kilometers north of Sebeș, along the Sebeș river in the Sebeș Formation dating from the early Maastrichtian, and was given the preliminary field number SbG/A-Sk1. Later it received the holotype inventory number EME VP.313. The discovery was made by the geologist and paleontologist Mátyás Vremir of the Transylvanian Museum Society of Cluj Napoca who sent them for analysis to Zoltán Csiki of the University of Bucharest. The findings were described on August 31, 2010, in the Proceedings of the National Academy of Sciences. The 1997 specimens indicate an individual about 45% longer than the holotype; they were also found in a younger stratum.

The generic name Balaur (three syllables, stressed on the second /a/) is from the Romanian word for a dragon of Romanian folklore, while the specific epithet bondoc (meaning "a squat, chubby individual") refers to the small, robust shape of the animal. As the mythological creature Balaur is a winged dragon, the name additionally hints at the close relation of the genus Balaur to the birds within Panaves. The species name bondoc was chosen by the discoverers also because it is derived from the Turkish bunduk, "small ball", thus alluding to the probable Asian origin of the ancestors of Balaur.

Balaur is a genus of theropod dinosaurs estimated to have lived about 70 million years ago in the late Cretaceous (Maastrichtian), and contains the single species B. bondoc. The bones of this species were shorter and heavier than those of basal paravians. While the feet of most early paravians bore a single, large "sickle claw" on the second toe which was held retracted off the ground, Balaur had large retractable sickle claws on both the first and second toes of each foot. In addition to its strange feet, the type specimen of Balaur is unique for its status of being the most complete theropod fossil from the late Cretaceous of Europe. It also possesses a great number of additional autapomorphies, including a reduced and presumably nonfunctional third finger, consisting of only one rudimentary phalanx.

The partial skeleton was collected from the red floodplain mudstone of the Sebeș Formation of Romania. It consists of a variety of vertebrae, as well as much of pectoral and pelvic girdles, and a large part of the limbs. It is the first reasonably complete and well-preserved theropod from the Late Cretaceous of Europe.

It is similar in size to Velociraptor, with Balaur's recovered skeletal elements suggesting an overall length of around 1.8–2.5 m (5.9–8.2 ft) and a body mass of 15 kg (33 lb). Balaur had re-evolved a functional first toe used to support its weight, which bore a large claw that could be hyperextended. It had short and stocky feet and legs, and large muscle attachment areas on the pelvis which indicate that it was adapted for strength rather than speed. Csiki et al. describe this "novel body plan" as "a dramatic example of aberrant morphology developed in island-dwelling taxa." The stocky feet are exemplified by the length of the metatarsus being only two times its width. It is 1.5 times wider than the lower leg. Both traits are unique in the Theropoda. The skeleton of Balaur also shows extensive fusion of limb bones. Wrist bones and the metacarpals are fused into a carpometacarpus. The pelvic bones are fused. The shinbone, calf bone and the upper ankle bones have been fused into a tibiotarsus and the lower ankle bones and the metatarsals into a tarsometatarsus. The degree of fusion is typical for the Avialae, the evolutionary branch of the birds and their direct relatives.