The Maldegem Formation (Dutch: Formatie van Maldegem; old name: Kallo Complex) is a geologic formation in the Belgian subsurface. The formation consists of alternating marine clay and sand strata, deposited during the late Eocene.
The Maldegem Formation crops out in the provinces of East Flanders and West Flanders and in the area between the Zenne and Dender rivers. In the northern parts of Flanders it forms an up to 50 meters thick sequence in the subsurface. Further south and to the east (in the Campine of the province of Antwerp) the formation pinches out and can be only a few meters in thickness.