The need for efficient, lightweight, flexible, stable and eco-friendly portable electric power delivery has placed research on supercapacitor electrode materials at the forefront of endeavors to provide future energy storage. Graphene-based materials and composites have been shown to be promising materials toward this goal. In this review, we describe recent progress in the development of electrode materials by the covalent functionalization of graphene. Covalent graphene derivatives are an emerging and potentially large class of very efficient materials, whose structural and physicochemical properties can be tailored according to the specific needs of capacitive charge storage. They also open doors to new composites and hybrids, which may further advance the field-encoding properties and other features as yet unexplored.