| Named By: | Merriam in 1895 |
| Time Period: | Middle-Late Triassic, 235.0-205.6 Ma[1] |
| Location: | USA, California - Mount Shasta. Canada, British Columbia - Pardonet Formation. China |
| Size: | 21 meters long for S. sikanniensis, other species like S. liangae seem to be 4 to 9 meters long based upon available fossils |
| Diet: | Specialist of soft bodied cephalopods like squid |
| Fossil(s): | Many specimens, although often incomplete and fragmentary |
| Classification: | | Chordata | Reptilia | Ichthyosauria | Shastasauridae | |
| Also known as: | | Shastasaurus alexandrae | Shastasaurus osmonti | Guanlingsaurus liangae | Shonisaurus sikanniensis | |
Shastasaurus ("Mt. Shasta lizard") is an extinct genus of ichthyosaur from the middle and late Triassic, and is the largest marine reptile that has yet been found. Specimens have been reported from the United States, Canada, and China.