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.