Environmental externalities of the Anthropocene—mainly generated from population growth, rapid urbanization, high private motor vehicle dependency, the deregulated market, mass livestock production, and excessive consumerism—have placed serious concerns for the future of natural ecosystems, which we are a part of. For instance, global climate change—the biggest challenge we have ever faced—is directly impacting wellbeing, and even the existence of humankind, in the long run. During the last two decades, the notion of the smart city—particularly the sustainable development of smart cities—has become a popular topic not only for scholars, particularly in the fields of technology, science, urban and environmental planning, development, and management, but also for urban policymakers and professional practitioners. This was due to digital technologies becoming a powerful enabler in stimulating paradigmatic shifts in urban development-related visions, strategies, implementation, and learning. This paper offers a critical review of the key literature on the issues relating to approaches, advances, and applications in the sustainable development of smart cities. It also introduces contributions from the Special Issue, and speculates on the prospective research directions to place necessary mechanisms to secure a smart and sustainable urban future for all.