Developmental dyslexia is a common neurodevelopmental disorder, affecting approximately 10% of the population. The defining feature of dyslexia is severe difficulties in reading and writing, although the precise manifestation of these difficulties varies according to the language that the child is learning to read. There has been a substantial research effort over recent decades to identify the causes of these literacy difficulties at the genetic, neural, sensorimotor, and cognitive levels. Current conceptualizations of dyslexia recognize an important role for oral language—and particularly phonological awareness—as a causal factor, and there has been considerable success in developing effective interventions on the basis of this. However, there is also increasing recognition that a multiple-deficit account is necessary to fully account for the individual variation documented within populations with dyslexia, and the frequent co-occurrence with other neurodevelopmental disorders.