The development of Information and Communication Technologies (ICT) enables the anywhere, anytime, and anything access, and has enhanced the quality of our life to a large extent. However, the other side is ever-increasing carbon emissions and severe environmental problems caused by the operational and computational cost of the fast-growing number of electronic devices. In this setting, there is a critical need of cooperating the green considerations into the solution design, development, and operation of hardware, network, and software systems. In fact, greenness is an urgent need for reducing carbon dioxide generation and optimizing energy consumption nowadays. Greenness covers a wide range of green topics, including green communication networks, green computing, and green software systems. This special issue dedicates to the research challenges and issues in novel greenness-aware engineering principles, methodologies, and tools about green networking, computing, and software systems