Carbonate facies and sequence stratigraphic analyses of the Upper Cretaceous successions from the western External Pyrenees were used to reconstruct palaeogeography and palaeoenvironments. Two third-order sequences can be recognised, showing the sedimentary evolution during the Late Cretaceous. At the beginning of the deposition of Sequence 1 (around the Santonian-Campanian boundary) the region was flooded, and the setting of a carbonate platform took place. From earliest to late Campanian, offshore bars developed at the western and eastern edges of the platform, while in the more open platform areas rudists, collonial corals and benthic foraminifera occurred. During the deposition of Sequence 2 (Late Campanian-early Maastrichtian?) sea level fell, and sediments of the continental Garumnian facies was deposited.