| Named By: | N.I. Novozhilov in 1964 |
| Time Period: | Jurassic |
| Location: | England |
| Size: | Almost 4 meters long |
| Diet: | Piscivore |
| Fossil(s): | Almost complete |
| Classification: | | Chordata | Reptilia | Sauropterygia | Plesiosauria | Pliosauridae | |
| Also known as: | | Plesiosaurus rostratus | |
Archaeonectrus is an extinct genus of pliosaur from the Jurassic of what is now southeastern England. The type species is Archaeonectrus (originally "Plesiosaurus") rostratus, first named by Sir Richard Owen in 1865, which was moved to its own genus by N.I. Novozhilov in 1964.