The Maastricht Formation (Dutch: Formatie van Maastricht; abbreviation: MMa), named after the city of Maastricht, the Netherlands, is a geological formation in the Netherlands and Belgium whose strata date back to the Late Cretaceous, within 500,000 years of the Cretaceous–Paleogene boundary, now dated at 66 million years ago. The formation is part of the Chalk Group and is between 30 and 90 metres (98 and 295 ft) thick. It crops out in southern parts of Dutch and Belgian Limburg and adjacent areas in Germany. It can be found in the subsurface of northern Belgium and southeastern Netherlands, especially in the and . Dinosaur remains are among the fossils that have been recovered from the formation.