This set of 49 volumes constitutes the proceedings of all of the conferences affiliated with HCI International 2020, which was held during July 19-24, 2020. The total of 1439 papers and 238 posters were carefully reviewed and selected from 6326 submissions. The respective focus of the 21 conferences is as follows: Human-Computer Interaction; Human Interface and the Management of Information; Engineering Psychology and Cognitive Ergonomics; Universal Access in Human-Computer Interaction; Virtual, Augmented and Mixed Reality; Cross-Cultural Design; Social Computing and Social Media; Augmented Cognition; Digital Human Modeling and Applications in Health, Safety, Ergonomics and Risk Management; Design, User Experience, and Usability; Distributed, Ambient and Pervasive Interactions; Learning and Collaboration Technologies; HCI in Business, Government and Organizations; Human Aspects of IT for the Aged Population; HCI for Cybersecurity, Privacy and Trust; HCI inGames, HCI in Mobility, Transport and Automotive Systems; Adaptive Instructional Systems; Culture and Computing; Design, Operation and Evaluation of Mobile Communications; and Artificial Intelligence in HCI.  The set therefore provides readers with a comprehensive overview of ongoing research and development within the broad field of Human-Computer Interaction. The list of individual volumes can be found under 2021 at https://link.springer.com/conference/hcii.