The magnetic field of Mars is the magnetic field generated from Mars's interior. Today, Mars does not have a global magnetic field. However, Mars did power an early dynamo that produced a strong magnetic field 4 billion years ago, comparable to Earth's present surface field. After the early dynamo ceased, a weak late dynamo was reactivated (or persisted up to) ~3.8 billion years ago. The distribution of Martian crustal magnetism is similar to the Martian dichotomy. Whereas the Martian northern lowlands are largely unmagnetized, the southern hemisphere possesses strong remanent magnetization, showing alternating stripes. Scientific understanding of the evolution of the magnetic field of Mars is based on the combination of satellite measurements and Martian ground-based magnetic data.