Due to urbanization, smart cities are emerging as a priority for research and development across the world. However, the rapid progress in smart cities research is posing enormous challenges in terms of the large amounts and various types of data at an unprecedented granularity, speed, and complexity that are increasingly produced by IoT sensors via emerging communication technologies. Meanwhile, the accumulation of huge amounts of data can be used to support intelligent decisions for better lives. Therefore, smart cities are data-driven. But effective computing, like distributed and parallel computing, artificial intelligence, and cloud/fog computing are the basic infrastructure for data processing, especially big data processing, and are the key factors for success in future smart cities. The use of big data can certainly help in creating cities where infrastructure and resources are used in a more efficient manner. The articles in this special section explore emerging trends, issues, and challenges in big data and its implementation toward future smart cities.