The Ilimaussaq intrusive complex is a large alkalic layered intrusion located on the southwest coast of Greenland. It is Mesoproterozoic in age, about 1.16 Ga. It is the type locality of agpaitic nepheline syenite and hosts a variety of unusual rock types.^[1]

The complex is noted for a wide variety of rare minerals and is the type locality for thirty minerals, including: aenigmatite, arfvedsonite, sodalite, eudialyte and tugtupite.^[2]

The complex has an areal extent of 8 by 17 km and an exposed thickness of 1700 m. The complex includes Kvanefjeld, a uranium deposit and a large reserve of rare-earth elements, zirconium, niobium and beryllium.^[1]