Bucking is a movement performed by an animal in which it lowers its head and raises its hindquarters into the air while kicking out with the hind legs. It is most commonly seen in herbivores such as equines, cattle, deer, goats, and sheep. Most research on this behavior has been directed towards horses and cattle.

Bucking can vary in intensity from the animals' slight elevation of both hind legs, to lowering their head between their front legs, arching their back, and kicking out several times. Originally, it was predominantly an anti-predator and play behavior, but with domestication, it is now also a behavioral issue in riding horses, and a desired behavior in bucking horses and bulls. If powerful, it may unseat or even throw off a rider, and can seriously injure either animal, rider, or both.

Bucking, though a potentially dangerous disobedience when under saddle, is a natural aspect of horse behavior. Bucking is used by animals for several reasons. In the wild, it can be used as a defense mechanism against predators such as mountain lions that attack by leaping on the animal’s back. By performing this behaviour, the animal throws a predator from its back. It can also be used as a mechanism of play and territorial herd defense.

For a human to safely ride a horse, the horse has to be desensitized to the presence of something on its back and also learn not to kick out with both hind legs while under saddle. Nonetheless, because the instinct is always there, bucking can still occur for a number of reasons:

Ordinary riders need to learn to ride out and correct a simple buck or two, because it is a relatively common form of disobedience. Further, at times, movement akin to bucking is actually required of a horse: Horses that are jumping over an obstacle actually are using almost the same action as bucking when launching themselves into the air, it is simply carried out with advanced planning over a higher and wider distance. The classical dressage movement known as the Capriole is also very similar to the low buck done by a horse when it kicks out with both hind legs.

Bucking in horses, especially if triggered by fear, pain or excitement, is generally a minor disobedience, unless it is strong enough to unseat the rider, at which point it is a dangerous act. If bucking is a premeditated act of the horse and becomes an undesired habit (such as when a horse learns to buck off a rider so as to no longer have to work), then the horse must be re-schooled by a professional trainer.

It is important to address the problem of the bucking immediately. Even with good cause, it is a potentially dangerous disobedience that cannot be encouraged or allowed to continue. However, a rider does need to be sure that it is not triggered by pain or poor riding. The horse's turn-out schedule should also be assessed, as extra turn-out will give a horse to release extra energy before a rider gets on. In certain cases (such as a show, when horses are unable to be turned-out for extended periods), longeing the horses for a brief period can help calm excess energy, allowing the rider to mount, and ride safely.

If poor riding is the cause, special attention and improvement to the rider’s balance and aids will help eliminate confusion and thus prevent the behavior. If ill-fitting equipment is the problem, a refit of the tack causing the discomfort is necessary to not only stop the bucking, but also to prevent further injuries that may arise due to poor fit.