Impact cratering has affected the surfaces of all bodies in our Solar System. These short-duration but energetic events can drastically affect the regional and occasionally the global environment of a planet. The cratering record is better preserved on Mars than on Earth due to longer-term stability of the Martian crust and lower degradation rates. Impact cratering had its greatest effect early in Solar System history when bombardment rates were higher than today and the sizes of the impacting objects were larger. The record from this period of time is largely lost on Earth. High bombardment rates early in Solar System history may have eroded the Martian atmosphere to its present thin state, causing dramatic climate change. The regolith covering much of the Martian surface and the large quantities of dust seen in the atmosphere and covering much of the ground have been attributed to fragmentation of target material by impacts. Heating associated with crater formation may have contributed volatiles to the Martian atmosphere and initiated some of the outflow channels. The effects of an impact event extend far beyond the crater rim, and the planet’s volatile-rich environment likely contributes to the greater ejecta extents seen on Mars than on the Moon. The cratering record of Mars thus holds important implications for how impacts may have affected the geologic evolution of Earth.