A sleep disorder (somnipathy) is a disorder in the sleep patterns of an individual. Some sleep disorders can interfere with mental and emotional function. A test commonly ordered for some sleep disorders is the polysomnogram.

The most common sleep disorders include:

Bruxism: The sufferer involuntarily grinds his or her teeth while sleeping.
Delayed sleep phase syndrome (DSPS): A sleep disorder of circadian rhythm, characterized by the inability to wake up and fall asleep at the desired times, but not by inability to stay asleep.
Hypopnea syndrome: Abnormally shallow breathing or slow respiratory rate while sleeping.
Insomnia: characterized by an inability to sleep and/or inability to remain asleep for a reasonable period.
Narcolepsy: The condition of falling asleep spontaneously and unwillingly.
Night terror or Pavor nocturnus or sleep terror disorder: abrupt awakening from sleep with behavior consistent with terror.
Parasomnias: Include a variety of disruptive sleep-related events.
Periodic limb movement disorder (PLMD): Involuntary movement of arms and/or legs during sleep. See also Hypnic jerk, which is not a disorder.
Rapid eye movement behavior disorder (RBD): Acting out violent or dramatic dreams while in REM sleep.
Restless legs syndrome (RLS): An irresistible urge to move legs while sleeping. Often accompanies PLMD.
Shift work sleep disorder (SWSD).
Sleep apnea: The obstruction of the airway during sleep.
Sleepwalking or somnambulism: Engaging in activities that are normally associated with wakefulness (such as eating or dressing), which may include walking, without the conscious knowledge of the subject.
Snoring: Loud breathing patterns while sleeping, sometimes accompanying sleep apnea.