Limaysaurus includes a single type species, Limaysaurus tessonei, which was originally referred to the genus Rebbachisaurus as Rebbachisaurus tessonei by Jorge Calvo and Leonardo Salgado in 1995. The genus Limaysaurus was named in 2004 by Salgado, Alberto Garrido, Sergio Cocca and Juan Cocca. The generic name is derived from the Río Limay. The holotype specimen, MUCPv-205, a partial skeleton including the back of the skull, was found in 1988 by Lieto Francisco Tessone, who is honoured in the specific name. It was afterwards collected, together with MUCPv-206, a second fragmentary skeleton, by José Bonaparte. Additional material referred to Limaysaurus was uncovered between 1995 and 2002 from the Puesto Quiroga Member of the Lohan Cura Formation at Cerro Aguada del León in the south-central part of Neuquén Province, Patagonia, Argentina. These beds appear to date from the Aptian-Albian interval.
Limaysaurus was a medium-sized sauropod. Gregory S. Paul in 2010 estimated its length at fifteen metres and its weight at seven tonnes. The neural spines on its back were very tall.