This book constitutes the refereed proceedings of the 6th International Conference on Information and Knowledge Systems, ICIKS 2023, held in Portsmouth, UK, during June 22–23, 2023. The 18 full papers and 6 short papers included in this book were carefully reviewed and selected from 58 submissions. They were organized in topical sections as follows: Decision Making, Recommender Systems, and Information Support Systems; Information Systems and Machine Learning; Knowledge Management, Context and Ontology; Cybersecurity and Intelligent Systems; and Natural Language Processing for Decision Systems.