This Open Access book LNCS 2719 constitutes the proceedings of the Second International Summit on the Global Internet of Things and Edge Computing, GIECS 2025, held in Madrid, Spain, on September 22, 2025. The 14 full papers included in this volume were carefully reviewed and selected from 21 submissions. They were organized into the following topical sections: Smarter IoT: Energy, Connectivity & Real-World Impact Building Trust: Privacy, Security & Responsible AI Data Spaces & Digital Infrastructure for the IoT Era Sustainable Solutions & Applied IoT Innovation