The three-volume set CCIS 2771-2773 constitutes the proceedings of the 27th International Conference on Human-Computer Interaction, HCII 2025, held in Gothenburg, Sweden, during June 22–27, 2025.A total of 7972 individuals from academia, research institutes, industry, and government agencies from 92 countries submitted contributions. 1430 papers and 355 posters (as short research papers) were included in the volumes of the proceedings published just before the start of the conference. Additionally, 439 papers and 104 posters were included in the volumes of the proceedings published after the conference, as “Late Breaking Work”.The papers were organized in topical sections as follows:Part I: Games, Learning, and Location-Based Technologies; Digital Innovation in Cultural Heritage; Health, Wellbeing, and Assistive TechnologiesPart II: Smart Mobility and Transportation; AI-Powered and Decision Support Systems; Innovations for Healthcare and Inclusive Design; Human-Centered Interaction Design and ExperiencePart II: Artificial Intelligence for Creativity, Education, and Design; Security, Privacy, and Social Impact; Advances in Immersive and Multimodal Interaction