This volume constitutes the proceedings of Third International Conference on Artificial Intelligence of Things and Systems, AIoTSys 2025, held in Lanzhou, China, during August 15–17, 2025. The 37 full papers included in this book were carefully reviewed and selected from 88 submissions. These papers discuss the integration of AI into IoT (AIoT) and its impact across a wide range of economic and social domains, driving the transformation of traditional industries into a new era of intelligence that goes beyond mere digitization and connectivity.