Falcarius (meaning "sickle cutter") is a genus of primitive therizinosaur dinosaur that lived during the Early Cretaceous period in what is now North America.

Unlike advanced therizinosaurs, Falcarius had a propubic pelvis and three-toed feet with a reduced hallux (first digit).

Falcarius is the basal most known definitive therizinosaurian genus, and has been considered a transitional form connecting the typical theropod bodyplan to the unusual morphology of Therizinosauridae.

The remains of Falcarius were first discovered in 1999 by commercial fossil collector Lawrence Walker at the Crystal Geyser Quarry site in Grand County.

Two extensive bone beds were discovered, including the remains of hundreds, perhaps thousands, of individuals of the new species.

[5] The first remains were partially described and discussed in 2004 on several abstracts by paleontologists Lindsay E. Zanno, then a doctoral student at the university, James I. Kirkland, Scott D. Sampson, chief curator at the University of Utah's Utah Museum of Natural History, Donald D. DeBlieux, David K. Smith and R. Kent Sanders.

[3][9] Zanno subsequently and informally described Falcarius as "the ultimate in bizarre: a cross between an ostrich, a gorilla, and Edward Scissorhands.

The holotype specimen, UMNH VP 15000, consists of a partial braincase and a large number of paratypes were assigned.

With its long neck, Falcarius could apparently reach about 1.5 m (4.9 ft) off the ground to munch leaves or fruit, possibly higher.

The front-most five teeth of the lower jaw are much longer, straighter and more pointed though, and might indicate a partially omnivorous diet including meat, e.g. small animals such as lizards.

The large skull opening in the snout, the fenestra antorbitalis, is positioned in a depression which reaches the side of the nasal bone.

The relatively large, and slightly recurved, pointed ten- to thirteen-centimeter (four- to five-inch) hand claws were likely used in self-defence.

On the thumb claw the raised attachment point for the tendon of the extensor muscle is bordered by deep grooves for ligaments.

In the arm, the shaft of the humerus is reinforced by powerful, somewhat obliquely placed, thickenings extending towards the condyles of the lower joint, which swellings have a hollow front edge.

The group is characterized by wider hips, a comparatively large braincase and long necks typical of plant eaters.

Falcarius shared some derived traits with the therizinosaurids: it had a long neck, small head with teeth adapted for eating plant material, a more robust arm with large hand-claws and a more vertical position of the body.

[4] The cladogram below shows the results of a phylogenetic analysis of Therizinosauria performed by Yoshitsugu Kobayashi and team in 2022, based on their description of Paralitherizinosaurus.