This proceedings presents the papers from Urb-IoT 2018 - 3rd EAI International Conference on IoT in Urban Space, which took place in Guimarães, Portugal on 21-22 November 2018. The conference aims to explore the emerging dynamics within the scope of the Internet of Things (IoT) and the new science of cities.The papers discuss fusion of heterogeneous urban sources, understanding urban data using machine learning and mining techniques, urban analytics, urban IoT infrastructures, crowd sourcing techniques, incentification and gamification, urban mobility and intelligent transportation systems, real time urban information systems, and more. The proceedings discuss innovative technologies that navigate industry and connectivity sectors in transportation, utility, public safety, healthcare, and education. The authors also discuss the increasing deployments of IoT technologies and the rise of the so-called 'Sensored Cities'' which are opening up new avenues of research opportunities towards that future.