Sleep is a fundamental biological process observed throughout the animal kingdom, and its disruption has devastating health consequences. Using a combination of optogenetics, electrophysiology, imaging, and gene expression profiling, we identify key neurons in the sleep control circuits and map their synaptic connections. Sleep appears to be controlled by a highly distributed network spanning the forebrain, midbrain, and hindbrain, where REM and non-REM sleep neurons are part of the central somatic and autonomic motor circuits. The intimate association between the sleep and autonomic/somatic motor control circuits suggests that a primary function of sleep is to suppress movement and promote processes incompatible with motor activity.