Libonectes is a prehistoric genus of sauropterygian reptile within the plesiosaur order. Fossil remains of Libonectes have been discovered in the Britton Formation of Texas (USA) and the Akrabou Formation of Morocco, with their origins traced back to the lower Turonian stage of the late Cretaceous era.

The Greek prefix "libo," signifying "southern" in English, combines with the Greek suffix "nectes," meaning "swimmer," to form the name Libonectes. Thus, Libonectes can be understood as "southern swimmer." This elasmosaurid plesiosaur is well represented by numerous findings in the southern regions of North America.

Libonectes, a plesiosaur of medium size, boasted a total length of 7.2 meters (24 ft) for the complete specimen. The type specimen, attributed to an individual with a neck measuring 5.06 meters (16.6 ft) in length, exhibited striking resemblance to the closely related Thalassomedon. However, there were distinct variations in the neck vertebrae structure, characterized by taller neural spines and extended supporting processes, while its skull featured nostrils positioned slightly closer to the tip.

The dental arrangement of Libonectes hints at a potential carnivorous inclination, although the inclusion of gastroliths within certain discovered fossils raises the possibility of an omnivorous dietary preference (though it's worth noting that plesiosaurs might have employed gastroliths for buoyancy regulation). The presence of these gastroliths could also imply that Libonectes consumed its prey whole. This aquatic creature likely pursued its hunting endeavors in deeper waters, possibly preying upon small fish and ammonites, given its presumed avoidance of shallower areas due to its substantial size. Furthermore, its leisurely swimming pace might have prompted Libonectes to utilize its considerable bulk to ensnare prey.