This book constitutes the refereed proceedings of the 4th International Conference on Intelligent Technologies and Applications, INTAP 2021, held in Grimstad, Norway, October 11–13, 2021. The 33 full papers included in this book were carefully reviewed and selected from 243 submissions. They were organized in topical sections as follows: Intelligence, Decision support systems, IoT; Robotics; ML and AI for Intelligent Health, Applications of intelligent technologies in Emergency Management; Smart Electrical Energy Systems, AI and ML in Security; ML and AI for sensing technologies, Social Media Analytics; ML in energy sectors and materials; and Miscellaneous.