The Landen Formation (abbreviation: LA) is a lithostratigraphic unit (a set of rock strata) in the subsurface of the Netherlands. This formation shares its name with the Belgian Landen Group, but the Belgian unit is thinner and has different definitions. 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.