This book constitutes the refereed proceedings of the 5th International Symposium on Ubiquitous Networking, UNet 2019, held in Limoges, France, in November 2019.The 17 revised full papers presented together with 1 short paper were carefully reviewed and selected from 41 submissions. The papers are organized in topical sections: ubiquitous communication technologies and networking; ubiquitous Internet of things; pervasive services and applications.