It is known from a partial skull and skeleton found in the late Maastrichtian-age Tremp Formation of the Pyrenees Mountains in Spain.

The type species is A. ardevoli, described in 2009 by Pereda-Suberbiola et al., a group of researchers from Spain.

The genus name refers to Arén, where it was found, and the specific epithet honours geologist Lluís Ardèvol.

[1] Arenysaurus was a lambeosaurine, a member of the hadrosaurid subfamily with hollow and decorative cranial crests.

[1][3] Its fossils were found in a small village (350 inhabitants) in the Aragonese Pyrenees called Arén (Areny in Catalan).