The objective of this Special Issue, “Hydraulic Behavior of Karst Aquifers”, is to focus on recent advances in karst hydrogeology in different areas of the world, focusing on topics dealing with the peculiar characteristics of karst aquifers. In particular, thirteen peer-reviewed articles were collected, focusing on hydraulic aspects and their relationship with geological features, geochemical and bacteriological aspects, tunneling and engineering mining inrush, and forecasting water resources and drought occurrences. Overall, these contributions describe several aspects of karst aquifers and are of great value for water resource management and protection.