Impulsivity is a multifaceted concept that captures an inability to wait, a preference for risky outcomes, a tendency to act without forethought, an insensitivity to consequences, and/or an inability to inhibit inappropriate behaviors. Because it touches on so many different aspects of behavior, impulsivity connects to a number of other concepts including patience, self-control, delay of gratification, intertemporal choice, discounting, risky choice, risk taking, inhibitory control, and sensation seeking. Therefore, researchers have created a taxonomy that carves up the concept into different types of impulsivity. A primary distinction divides impulsivity into impulsive choice (or decision making) and impulsive action (or disinhibition) based on both behavioral correlates across tasks and neural mechanisms. Due to the many different varieties of impulsivity, this concept is of relevance to a large number of fields, including psychology, economics, biology, neuroscience, anthropology, nutrition, finance, and environmental sciences. The current volume reflects the scope of impulsivity by including contributors from a wide range of fields who work across levels of analysis, species, and timescales to understand the many faces of impulsivity.