Kallithea is a suburb located within the Athens agglomeration and serves as a municipality in the south Athens regional unit of Greece. It ranks as the eighth largest municipality in the country and the fourth largest within the Athens urban area.
The municipality covers an area of 4.749 km2 (1.834 sq mi). It is characterized by high population density, ranking as the second most densely populated municipality in Greece and one of the most densely populated cities globally, with a density of 20,240/km2 (52,400/sq mi).