| Named By: | Gasparini in 1997 |
| Time Period: | Middle Jurassic |
| Location: | Argentina, Los Molles Formation |
| Size: | Uncertain |
| Diet: | Piscivore/Carnivore |
| Fossil(s): | Complete skull and mandible (lower jaw) and some cervical (neck) vertebrae |
| Classification: | | Chordata | Reptilia | Sauropterygia | Plesiosauria | Rhomaleos | |
Maresaurus is an extinct genus of pliosaur from the Middle Jurassic (Bajocian) of what is now Argentina. The type species, Maresaurus coccai, was named by Gasparini in 1997. Recent phylogenetic analysis found Maresaurus to be a rhomaleosaurid.