Nili Fossae is a fracture in the surface of Mars that has been eroded and partly filled in by sediments and clay-rich ejecta from a nearby crater. It is located at ≈22°N, ≈75°E and has an elevation of −0.6 km. The region dates from >3.5 Ga (the Noachian epoch).

The largest exposure of olivine on the planet is located here.

Nili Fossae has been considered as a possible landing site for the Mars Science Laboratory.