This nine-volume set LNCS 15473-15482 constitutes the proceedings of the 26th International Conference, HCI International 2023, in Washington, DC, USA, in June/July 2024. For the HCCII 2024 proceedings, a total of 1271 papers and 309 posters was carefully reviewed and selected from 5108 submissions. Additionally, 222 papers and 104 posters are included in the volumes of the proceedings published after the conference, as "Late Breaking Work". These papers were organized in the following topical sections: HCI Theories, Methods and Tools; Multimodal Interaction; Interacting with Chatbots and Generative AI; Interacting in Social Media; Fintech, Consumer Behavior and the Business Environment; Design for Health and Wellbeing; Ergonomics and Digital Human Modelling; Virtual Experiences in XR and the Metaverse; Playing Experiences; Design for Learning; New Cultural and Tourism Experiences; Accessibility and Design for All; Design for Older Adults; User Experience Design and Evaluation: Novel Approaches and Case Studies; Safety, Security and Privacy; HCI in Automated Vehicles and Automotive; HCI in Aviation, Transport and Safety; Human-Centered AI; AI for Decision Making and Sentiment Analysis.