This book presents the proceedings of the 12th Intelligent Systems Conference 2026 (IntelliSys 2026), held on September 3–4, 2026, in Amsterdam, The Netherlands, and contains selected peer-reviewed papers presenting recent advances, innovative methodologies, and practical applications in the field of intelligent systems and related technologies.The conference served as an international platform for researchers, academicians, scientists, and industry professionals to exchange ideas, share research findings, and discuss current challenges and future directions in intelligent computing. The accepted contributions cover a wide range of topics, including Artificial Intelligence, Machine Learning, Computer Vision, Internet of Things (IoT), Cyber-Physical Systems, Data Science, and Intelligent Computing. All submissions underwent a rigorous double-blind peer-review process conducted by the Technical Program Committee to ensure high standards of quality, originality, technical merit, and relevance to the conference themes.These proceedings reflect the multidisciplinary nature and continuing growth of intelligent systems research.