This book constitutes the proceedings of the 49th German Conference on Artificial Intelligence (Künstliche Intelligenz), KI 2026, which was held in Bremen, Germany, August 11–16, 2026, ProceedingsThe 12 full papers, 19 short papers and 1 extended abstracts presented in these proceedings were carefully reviewed and selected from 78 submissions. They focus on new research results on theory and applications in AI. The papers were categorized in the following sections: Full Technical Papers; Technical Communications; Extended Abstracts.