This entry critically examines attention deficit hyperactivity disorder (ADHD) as a disability situated at the intersection of education and psychiatry, focusing on how the construct evolved from early classifications of behavioural and cognitive differences in education to its eventual consolidation within legal frameworks and psychiatric nosology. The entry begins by defining ADHD and then describes how it is classified as a disability under equality legislation in the United Kingdom (UK), followed by an exploration of the historical events in education and psychiatry that contributed to establishing it as a psychiatric disorder. The tensions between the medical and social models of disability will be revealed, and evidence for the neurobiological basis of ADHD will be summarised, along with a critique of diagnostic gatekeeping, misinformation, and medicalisation. By presenting an inclusive perspective that redefines ADHD as an educational-psychiatric neurodivergence, the entry acknowledges ADHD can have both disabling effects and adaptive traits. By offering a critical synthesis of historical, current, and prospective viewpoints, this entry provides a detailed analysis of ADHD as a contemporary but controversial psychiatric disorder.