This book constitutes the refereed proceedings of the 23rd International Conference on Next Generation Wired/Wireless Networking, NEW2AN 2023, and the 16th Conference on Internet of Things and Smart Spaces, ruSMART 2023, held in Dubai, United Arab Emirates, in December 21-22, 2023. The 67 full papers included in the joint proceedings were carefully reviewed and selected from 258 submissions. They present a unique cross-disciplinary mixture of telecommunications-related research and science, various aspects of next generation data networks, while special attention is given to advanced wireless networking and applications.