Altirhinus (/ˌæltɪˈraɪnəs/; "high nose") is a genus of hadrosauroid ornithopod dinosaur from the Early Cretaceous period of Mongolia.

All known specimens of Altirhinus were recovered in 1981 during collaborative expeditions organized by Soviet and Mongolian scientists, from the Khuren Dukh Formation in the Dornogovi Province of Mongolia.

The Khukhtek was formed in the Aptian to Albian stages of the Early Cretaceous Period, which lasted from between 125 and 100.5 million years ago.

The holotype, PIN 3386/8, is a skull, which is well preserved on the left side, as well as some postcranial material consisting of pieces of the hands, feet, shoulder and pelvic girdles.

There is one known species (A. kurzanovi), which honors Sergei Kurzanov, the influential Russian paleontologist who originally found the specimens in 1981.

[1] The skull alone is about 760 mm long, with a wide mouth and a distinctive tall arch on top of its snout, from which this dinosaur derives its name.

More recent analyses all find Altirhinus more derived than either of those two genera, but less than Protohadros, Probactrosaurus, and hadrosaurids (Head, 2001; Kobayashi & Azuma, 2003; Norman, 2004).

The former two studies also place Eolambia between Altirhinus and hadrosaurids, while Norman's analysis finds that the two genera share a clade.

As only two skulls have been located, it is entirely possible that the arched snout is only found in one sex, in which case it may have been used for sexual display, like in modern-day elephant seals.