HCI 2020 is the 20th in a series of International Conference on the Physics of Highly Charged Ions. The conference covers the following topics on highly charged ions: Fundamental aspects, Structure and Spectroscopy; Collisions with Electrons, Ions, Atoms and Molecules; Interactions with Clusters, Surfaces and Solids; Interactions with Photons, Plasmas and Strong Field Processes; Production, Experimental developments and Applications.