Altirhinus (al-ti-RIEN-us; Meaning "High snout") is a genus of iguanodontian ornithopod dinosaur from the Early Cretaceous Period of Mongolia. It was herbivorous and bipedal when walking or running, but probably became quadrupedal when feeding from the ground. The entire body probably extended 26 feet (8 meters) from snout to tail tip. The skull alone is about 30 inches (760mm) long, with a wide mouth and a distinctive tall arch on top of its snout, from which this dinosaur derives its name.

The name was created in 1998 from a Latin word, altus ("high") and a Greek word, rhinos ("nose" or "snout"). There is one known species (A. kurzanovi), which honors Sergei Kurzanov, the influential Russian paleontologist who originally found the specimens in 1981.