The Castrillo de la Reina Formation is a geological formation in Spain.

It is late Barremian to early Aptian in age.

It interpreted as a fluvial deposit.

It primarily consists of red clay, with ribbon shaped sandstone channel fills.

The rebbachisaurid dinosaur Demandasaurus occurs in the formation,[1] alongside somphospondylan Europatitan[2] as well as indeterminate small ornithopods, iguanodonts (including members of the Hadrosauriformes[3]) and spinosaurids, the earliest known stem-rhabdodontid (indeterminate)[4] and the lizard Arcanosaurus.