Recent years have witnessed a dramatic increase in our ability to collect data from sensors and devices, across different formats, from connected applications and enormous dynamic networks including social networks, as well as many other sources. This data flood has outpaced our capability to process, analyze, store and understand these datasets using traditional methods. In all these areas, we are facing significant challenges in leveraging the vast amount of data, and dealing with its speed of arrival and its heterogeneous and evolving nature. This includes challenges in system capabilities, storage and processing, algorithmic design and business models. Approaches for dealing with data in a streaming fashion are thus becoming increasingly relevant in many tasks, including mining and analysis, data representation and visualization, incremental learning and anomaly detection. We are pleased to introduce this collection of papers in the special issue on Big Data, IoT Streams and Heterogeneous Source Mining. Earlier versions of these extended papers were presented at BigMine 17-a KDD 2017 workshop, which was held in Halifax, Canada, on 14 August 2017. After the workshop, we invited the authors of the longpresentation papers to submit an extended version of their B Jesse Read