The 3rd International Conference on Sustainable Communication Networks and Applications [ICSCN 2021] organized on 29-30 July, 2021 by Surya Engineering College (SEC), Erode, India at Erode - Perundurai Highway, Kathirampatti, Mettukadai, Erode,Tamil Nadu 638107. The main objective of ICSCN 2021 is to serve as a confluence point between researchers, academicians and industrialists to present their state-of-the-art research and works in the areas of sustainable communication networks and applications to materialize prodigious benefits in order to meet the global sustainable needs. The extensive goal of ICSCN 2021 is to promote a community-wide discussions identifying the up-to-date technologies and theories for sustainable computing and communication networks to address the emerging challenges and create a sustainable environment, green energy and network models, algorithms, platforms and tools required to facilitate the next-generation sustainable communication and networking infrastructure. The 3rd International Conference on Sustainable Communication Networks and Applications [ICSCN 2021] will be an intriguing platform for scientists, researchers, research scholars and industrialists to present, share and exchange their ideas on the recent advances in sustainable communication networks and applications.