Cities around the world are facing enormous strain to sustain and improve the quality of life (QoL) owing to rapid urbanization and rising populations. Management of urban resources in a responsible manner is key to sustainable development in rapidly urbanizing regions. Cities are increasingly making use of modern technologies with a focus on cost reduction, optimal resource utilization and creation of more liveable urban environment. Such cities, called smart cities, have gained traction with policy makers, politicians and urban managers having the attributes of sustainable urbanism, QoL, and smartness. Smart cities provide digital intelligence to existing cities by creating a ubiquitous, integrated and smart environment where IoT applications impart seamless interconnection, interaction, control and insights about the isolated systems within the cities. This paper discusses and reviews the role of IoT for sustainable smart cities by highlighting IoT applications for smart cities. The challenges and opportunities associated with IoT enabled smart cities are also highlighted.