| Named By: | Hector in 1874 |
| Time Period: | Late Cretaceous |
| Location: | New Zealand - Conway Formation. Antarctica, James Ross Island - Santa Marta Formation. Japan |
| Size: | Often cited at being 6 meters long, the addition of Tylosaurus haumuriensis has raised the prospect that Taniwhasaurus may have grown up to 12 meters long |
| Diet: | Carnivore |
| Fossil(s): | Several specimens, usually of scattered skull and post cranial remains |
| Classification: | | Chordata | Reptilia | Squamata | Scleroglossa | Mosasauridae | Tylosaurinae | |
| Also known as: | | Lakumasurus | Tylosaurus haumuriensis | |
Taniwhasaurus (from the Maori Taniwha, a supernatural, aquatic creature, and the Greek sauros/sauros, meaning lizard) is an extinct genus of mosasaur (carnivorous marine lizards) which inhabited New Zealand, Japan and Antarctica. The genus was a close relative of the genera Tylosaurus and Hainosaurus.