The Landen Formation (abbreviation: LA) is a lithostratigraphic unit (a set of rock strata) in the subsurface of the Netherlands.
The Landen Formation consists of shallow marine and lagoonal sediments (mostly clay, sandy clay and marl) from the late Paleocene to early Eocene (between 58 and 54 million years old).
Dutch stratigraphers see the Landen Formation as part of the Lower North Sea Group.
It is subdivided into five only regionally recognized members: Some of the sandy layers can have been made into sandstone by diagenetic processes.
The whole formation is interpreted as one megacycle: the lower parts (Swalmen and Orp) represent a marine transgression, while the upper parts (Reusel and Liessel) represent a regression.