Despite the considerable research effort in the area of Mobile and Ubiquitous Computing over the nearly two decades, and the maturity of some of its base technologies, many challenges persist. The goal of the eighteenth annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MobiQuitous 2023) is to provide a forum for presenting and discussing high-quality research in the field, involving international practitioners and researchers from diverse backgrounds. MobiQuitous 2023 will thus foster research collaboration through focused discussions, interaction and exchange of experiences that will designate future research efforts and directions. Areas addressed by the conference include systems, applications, social networks, middleware, networking, sensing, data management, data processing and services, all with special focus on mobile and ubiquitous computing.