The cerebellum is important for movement control and plays a critical role in balance and locomotion. As such, one of the most characteristic and sensitive signs of cerebellar damage is gait ataxia. How the cerebellum normally contributes to locomotor behavior is unknown, though recent work suggests that it helps generate appropriate patterns of limb movements, dynamically regulate upright posture and balance, and adjust the feedforward control of locomotor output through error-feedback learning. The purpose of this review is to examine mechanisms of cerebellar control of locomotion, emphasizing studies of humans and other animals. Implications for rehabilitation are also considered.