Dyssomnia is a broad category of sleep disorders characterized by disturbances in the amount, quality, or timing of sleep. The term encompasses a range of conditions in which the normal sleep-wake cycle is disrupted, making it difficult for the affected person to fall asleep, stay asleep, or achieve adequate restorative sleep. Dyssomnias are distinct from parasomnias, which involve abnormal behaviors or experiences during sleep. Dyssomnias are typically divided into three subgroups. Intrinsic sleep disorders arise from within the body and include insomnia, narcolepsy, idiopathic hypersomnia, restless legs syndrome, and periodic limb movement disorder. Extrinsic sleep disorders are caused by external environmental or behavioral factors, such as poor sleep hygiene, noise disturbances, altitude-related sleep disturbance, or the use of sleep-disrupting substances such as caffeine or alcohol. Circadian rhythm sleep disorders result from a misalignment between the body’s internal biological clock and the external environment, including jet lag, shift work disorder, delayed sleep phase disorder, and advanced sleep phase disorder. Symptoms of dyssomnia vary depending on the specific disorder but commonly include difficulty falling asleep, frequent or prolonged awakenings during the night, waking too early, sleeping for excessively long periods, daytime sleepiness, fatigue, and impaired daytime functioning. Treatment of dyssomnia depends on the underlying type and cause. Behavioral interventions such as cognitive behavioral therapy for insomnia (CBT-I), sleep hygiene education, and lifestyle modifications are commonly recommended. Medical treatments, including medication or device therapy (such as CPAP for sleep apnea), may be appropriate for specific disorders. Accurate diagnosis by a healthcare professional is the essential first step.