Lungeing or exercising a horse on the lunge is an exercise method that involves the horse moving in a circle around the handler/trainer holding a long line (the lungeing rein) attached to the horse's head. The lungeing rein can be attached to a lungeing cavesson, to a headcollar or to the bit rings of a bridle. The horse is controlled by the handler's voice, although a long 'lungeing' whip may be carried to encourage a horse to move forwards.

Lungeing is a way to exercise a horse (as an alternative to riding). Horses can be lunged in a saddle or in a roller and may be equiped specific training aids such as side-reins to encourage a particular way of going. Skilled handlers and trainers can use lungeing to train horses and build-up muscle. Lungeing is often used to familiarise a young horse with equipment and voice aids before they are first ridden. Lungeing can also be performed with a rider on the horse's back, allowing a trainer to correct and imporve a rider's position in the saddle.