| Named By: | Shikama, Kamei & Murata in 1978 |
| Time Period: | Early Triassic, 248-245 Ma |
| Location: | Japan, Canada |
| Size: | 3 meters long |
| Diet: | Piscivore |
| Fossil(s): | Few specimens |
| Classification: | | Chordata | Reptilia | Ichthyopterygia | |
Utatsusaurus is the earliest-known ichthyopterygian which lived in the early Triassic period (c. 245-250 millions years ago).It is nearly 3m (about 9 feet) long with a slender body. The first specimen was found in Utatsu-cho (now part of Minamisanriku-cho), Miyagi Prefecture, Japan. The name Utatsusaurus was given after the city. The fossils have been found from the Lower Triassic of Miyagi Prefecture, Japan and British Columbia, Canada.
Utatsusaurus is one of the most primitive grades of ichthyosaurs, a basal ichthyosaur.