Falcarius, meaning "sickle cutter," is a primitive therizinosaur dinosaur genus that inhabited North America during the Early Cretaceous period. Its fossils were initially uncovered in the Cedar Mountain Formation in 1999, with additional discoveries made in the 2000s. This genus is represented by various specimens, including individuals in different stages of development.

Falcarius was a bipedal herbivore measuring about 4 meters (13 feet) in length. It possessed a small head, an elongated neck, and tail. Distinguishing it from more advanced therizinosaurs, Falcarius had a propubic pelvis and three-toed feet with a reduced hallux (first digit).

Among therizinosaurs, Falcarius holds the position of the most basal and represents a transitional link between the typical theropod body plan and the distinctive features of the Therizinosauridae. Its formal description in 2005, following the discovery of the basal therizinosauroid Beipiaosaurus in China in 1999, significantly contributed to our understanding of the early evolution of Therizinosauria and their place within the broader group of Theropoda. As mentioned earlier Falcarius is regarded as a transitionary species among therizinosaurs, signifying a shift from carnivorous to herbivorous feeding habits. While some experts suggest it may have been an omnivore, the leaf-shaped teeth appear to be better adapted for herbivorous consumption.

The head structure of Falcarius remains only partially understood. It featured a small and elongated skull. Thanks to its extended neck, Falcarius had the capability to reach heights of approximately 1.5 meters (4.9 feet) above the ground, allowing it to feed on leaves or fruit. The upper jaw, or maxilla, was equipped with a minimum of sixteen teeth, while the lower jaw, or dentary, bore twenty-eight teeth. The small, leaf-shaped maxillary teeth, finely serrated, strongly suggest a plant-based diet for this dinosaur.