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.