Sinusonasus is a genus of dinosaurs from the Early Cretaceous Period, recovered from the Yixian Formation.

The type species, Sinusonasus magnodens, was named and described by Xu Xing and Wang Xiaolin in 2004.

[1] The generic name, derived from Latin sinus, "wave", and nasus, "nose", refers to the sinusoid form, in lateral view, of the nasals.

The holotype, IVPP V 11527, was found in the Lujiatun Member of the Yixian Formation, dating from the Hauterivian.

The chevrons on the rear caudal vertebrae are so long, measured from the front to the back, that they connect, forming a continuous plate at the underside of the tail.

This was by the describing authors not interpreted as an indication for a long ghost lineage, troodontids developing earlier during the Jurassic than had been thought, but explained by rapid evolutionary change after a Cretaceous origin of the group.