Sleep disorders are pervasive in patients with multiple sclerosis (MS) although clinically underrecognized by most physicians. The most common sleep disorders seen in patients with MS include insomnia, nocturnal movement disorders, sleep-disordered breathing, narcolepsy, and rapid eye movement sleep behavior disorder. Factors that influence the quality of sleep in this patient population include pain, nocturia, depression, medication effect, location of lesions, and disease severity. Disrupted sleep has the potential to cause daytime somnolence, increased fatigue, and nonrefreshing sleep, and it may be associated with dangerous respiratory events. Awareness and treatment of these conditions is vital to improving health and quality of life in patients with MS.