Tuarangisaurus (Māori: tuarangi "ancient" + Greek: σαῦρος, romanized: sauros "lizard") is an extinct genus of elasmosaurid known from New Zealand.

[1] It was on 20 March 1978 collected by amateur paleontologists from the Maungataniwha Sandstone Member of the Tahora Formation, dating to the upper Campanian to lower Maastrichtian stage of the Late Cretaceous.

[1] It can be distinguished from all other known elasmosaurids by a unique combination of characteristics as well as two otherwise unknown traits: the ectopterygoid has a long process directed towards the back, and a large boss of bone underneath.

[10] A phylogenetic analysis of plesiosaurs run by O'Gorman and colleagues in 2016 reaffirmed that Tuarangisaurus was an elasmosaurid, but rejected a close relationship with Callawayasaurus.

[2] Gronausaurus Speeton clay plesiosaur Wapuskanectes betsynicollsae Callawayasaurus colombiensis Styxosaurus snowii Futabasaurus suzukii Albertonectes vanderveldei Tuarangisaurus keyesi Thalassomedon haningtoni Elasmosaurus platyurus Terminonatator ponteixensis Hydrotherosaurus alexandrae Libonectes morgani Kawanectes lafquenianum Vegasaurus molyi Morenosaurus stocki Kaiwhekea katiki Aristonectes parvidens Aristonectes quiriquinensis