Orcus Patera is a region on the surface of the planet Mars. It is a depression about 380 km long, 140 km wide, and about 0.5 km (500 meters) deep but with a relatively smooth floor. It has a rim up to 1.8 km high. Orcus Patera is west of Mons Olympus and east of Elysium Mons. It is about half-way between those two volcanoes, and east and north of Gale crater.
It has experienced aeolian processes, and has some small craters and graben structures. However, it is not known how the patera originally formed. Theories include volcanic, tectonic, or cratering events.