Night eating syndrome (NES) was first described in the 1950s among persons seeking weight management but who were struggling to lose weight. The three main features included (1) a reduced appetite in the morning (morning anorexia), (b) increased consumption of food in the evening or after dinner hours (evening hyperphagia), and (c) insomnia. Waking to eat, now known as nocturnal ingestions, was added as a criterion in later years. This entry begins with a further definition of NES and then describes the prevalence, clinical features, assessment, and treatment of NES. The entry concludes with a discussion of its clinical significance.