The hippocampus is the term for an area at the base of the cerebrum, basal to each of the temporal lobes. Its gray matter has a peculiar C-shape that forms a bulge in the temporal horns of the lateral ventricles, and which has given rise to its name.

The hippocampus represents part of the cerebrum's limbic system and developmentally belongs to its oldest part (archicortex). The anterior part of the hippocampus was formerly called the ammon's horn (cornu Ammonis), but the abbreviation CA is still used as a designation for the division (CA1-4) of the hippocampus.

The hippocampus is found in the brain of all vertebrates. It plays an important role in learning and short-term memory, as well as consolidation of factual knowledge and for orientation, and it is therefore central to the problems surrounding Alzheimer's disease and other forms of dementia, without knowing how the connection occurs, since reduction of this cell area is not always proven . However, damage to the hippocampal cells can occur for other, different reasons (encephalitis, hypoxia, haemorrhages).