Thyles Rupes is a large cliff-like tectonic feature (rupes, coming from latin, meaning rocks, cliff or scarp) on Mars, located in the planet's southern high latitudes. "Thyles" refers to the legendary land of Thule, a distant place beyond the edge of the known world in classical geography.  It is one of the more prominent scarps in the region surrounding the south polar area. Thyles Rupes is believed to be a tectonic feature, so it has formed through crustal deformation and faulting, where one block of Martian crust was pushed upward relative to another, creating a steep cliff. Such processes are initiated when a planet’s crust contracts as the planet cools internally, resulting in global contraction. The scarp extends for hundreds of kilometers and cuts across heavily cratered terrain, making it easy to identify in orbital images. Unlike Earth, Mars does not have active plate tectonics, so these scarps preserve evidence of ancient crustal movements that may be billions of years old.

Scientists have noted that impact craters intersect the scarp. By studying which features cut across others, geologists can determine the relative ages of the craters and the faulting event that formed Thyles Rupes. Evidence suggests the visible scarp developed after some of the surrounding terrain and craters were already in place.