Electroencephalography (EEG) research has traditionally been associated with a participant being seated at a table, with many electrodes affixed to a “swimming cap”, which in turn is connected to an amplifier connected to one or more computers. While this type of experimental setup affords the ability to ask an array of research questions, it also greatly restricts ecological validity among other factors. The advent of mobile EEG—EEG systems that are lightweight, easy to put on, and wireless—allows a researcher to take EEG research out of the laboratory and into the “real world”. In this chapter, we define what mobile EEG is and provide a brief historical context of the development of mobile EEG. We then look at the range of mobile EEG systems available to researchers, the technical considerations that need to be considered when using these systems, and provide thoughts on the validation of said systems. Finally, we end with an application section in which we describe a range of mobile EEG “use cases” to give the reader examples of how mobile EEG can be used.