The mammalian hippocampus is a conserved region and probably one of the best-studied brain areas. However, the homologous regions in other vertebrates differ in the anatomical organization, but are still able to perform similar functions. In this special topic issue, international experts in evolutionary neuroscience discuss the homology of the hippocampus among fishes, amphibians, reptiles, birds, and mammals. The articles cover the history of hippocampal research, developmental patterns of gene expression in mammals, birds and reptiles, and the internal connectivity in adult birds and mammals. Furthermore it explores the role of the hippocampus in spatial navigation and memory, as well as its role in social cognition and in regulating the stress response. In addition to evolutionary neuroscientists, this publication is of special interest to all those studying the mammalian hippocampus, as it puts their structure of interest in a wider evolutionary context. It will also be relevant to behavioral ecologists and other behavioral biologists interested in navigation and memory across a range of species.