Paleointensity is the variations in magnitude of the geomagnetic field in the near and remote past. Similar to paleodirectional studies, paleointensity research depends on the ability of a rock to preserve for a geologically long time the information related to the ambient magnetic field existing at the time the rock was formed.

Paleointensity determination is difficult because a quantitative relation should exist between the field strength and the remanent magnetization acquired in it. In contrast, for ordinary paleomagnetic studies seeking the direction of the paleofield, only a qualitative relation that the remanence direction is parallel to the magnetic field is required.